Here's an example SQL statement. mytable ) then the table is created in the specified schema. Apr 7, 2019 · ALTER TABLE patient ALTER COLUMN patientid SET NOT NULL; ALTER TABLE patient ADD CONSTRAINT uk_patientid UNIQUE (patientid); whenever you insert new rows such as. Syntax. Time: 579. Jun 27, 2024 · Ordinarily this is checked during the ALTER TABLE by scanning the entire table; however, if a valid CHECK constraint is found which proves no NULL can exist, then the table scan is skipped. Mar 16, 2024 · Adicionando uma nova coluna. scheme. AS. Mar 21, 2016 · 33. Of course any change of the constraint will be run against the current table data. You can get the name of the constraint by typing. 5. To add a column, use a command like: ALTER TABLE products ADD COLUMN description text; The new column is initially filled with whatever default value is given (null if you don't specify a DEFAULT clause). To add a column with a non-null default: ALTER TABLE measurements ADD COLUMN mtime timestamp with time zone DEFAULT now(); To add a column of type varchar to a table: ALTER TABLE distributors ADD COLUMN address varchar(30); That will cause all existing rows in the table to be filled with null values for the new column. alter table table_name alter column columname type decimal(16,2); for converting data type from int to decimal. Jul 15, 2015 · No reference to the referenced table name. The ALTER TABLE statement is also used to add and drop various constraints on an existing table. ALTER TABLE changes the definition of an existing table. In your case, it will be something like: CREATE OR REPLACE VIEW folders_contents. ADD COLUMN new_column_name column_definition. Postgres does not support adding multiple columns by one ALTER TABLE statement. If this table is a partition, one cannot perform DROP NOT NULL on a column if it is marked NOT NULL in the parent table. regression=# alter table foo add column "saveState" varchar (1) default '0'; ALTER TABLE. O nome da nova coluna é o nome da nova coluna a ser adicionada. Third, supply the new data type for the column after the TYPE keyword. ) Use CREATE OR REPLACE INSTEAD. 2 or later you can just rename the constraint as well (as dequis commented): May 27, 2022 · ALTER TABLE tasks ADD COLUMN in_progress BOOLEAN NOT NULL DEFAULT FALSE; The table tasks has less than 20,000 rows and is queried once every 5 minutes or so. 518 ms. To add a column with a non-null default: ALTER TABLE measurements ADD COLUMN mtime timestamp with time zone DEFAULT now(); Dec 31, 2018 · 1. example ADD COLUMN newcolumn UUID DEFAULT (uuid_generate_v4()); The DEFAULT clause will immediately fill the column with UUIDs. tables AS T WHERE T. Alternatively, you could add a serial or IDENTITY column to your table before importing data from your CSV and not assign it in the process, then it defaults to serial numbers automatically. for DEFAULT clause you must use bare value. To add a new column with some default value other than null, use the following ALTER TABLE syntax. answered Feb 12, 2015 at 15:27. t_my_table ADD COLUMN purshased_product jsonb; (You may also use the type json) Please check here to understand the diff. 0. Drop column in the table. My guess would be that it works even without the DROP DEFAULT since it's a single statement. The RENAME clause causes the name of a table or column to change without changing any of the data contained in the affected select table_name from user_tab_columns. What should work in any case is ALTER TABLE table_to_alter ALTER COLUMN table_id DROP DEFAULT, ALTER COLUMN table_id SET DATA TYPE UUID USING (uuid_generate_v4()), ALTER COLUMN table_id SET DEFAULT uuid_generate_v4();. May 28, 2021 · 1. But PostgreSQL has a non-standard extension that lets you use multiple constraint clauses in a single SQL statement. Use the AFTER directive to place it in a certain position within the table: ALTER table table_name Add column column_name57 integer AFTER column_name56 From mysql doc. How long it did depend on size of table. where table_name = myTable and column_name = myColumn; I am then testing whether the query returns anything so as to prove the column exists. when OR_ID is not null then MD5(cast(OR_ID as varchar(100))) when Asset_ID is not null then MD5(Asset_ID) else null. For example. Sep 30, 2021 · Auto increment table column; Triggers a whole-table rewrite, of course. 语法如下：. See also this related question ; it's about Rails migrations, but the underlying cause is the same and the answer applies. (No I had not tried it out). 它有好几种子形式：. Now do it: ALTER id DROP DEFAULT, ALTER id TYPE uuid USING uuid_generate_v4(), ALTER id SET DEFAULT uuid_generate_v4(); Mar 14, 2015 · 30. I had to: ALTER table ALTER COLUMN bar DROP DEFAULT; and then it worked. From documentation this example: ALTER TABLE distributors. . 添加列的语法. And numbers are assigned arbitrarily by current physical order of rows. CREATE TABLE will create a new, initially empty table in the current database. The following examples demonstrate the instant DDL feature. new_id value, at set it as default value for your address. To add a column with a non-null default: ALTER TABLE measurements ADD COLUMN mtime timestamp with time zone DEFAULT now(); The table has only 5,000 records, and I can't wait too much time since it block the access to the table. (If you want to modify the view's defining query, use CREATE OR REPLACE VIEW. I have a test database (equal to production), and it worked very quickly. Postgres will not actually rewrite the table because you provided a constant value (false) for the default value. There is no ALTER command for constraints in Postgres. Sep 18, 2013 · ALTER TABLE sensitivity ADD qc_isotope VARCHAR(2) DEFAULT 'TC' CHECK (qc_isotope IN ('TC', 'TL')) NOT NULL; The full list of syntax options etc for check constraints is described here. Jun 18, 2019 · You don't need the [DATA] TYPE part here (that's only needed when you want to change the type) : CREATE TABLE barf. name + ' ADD foo int NULL' FROM sys. ADD COLUMN column_name datatype column_constraint; Code language: SQL (Structured Query Language) (sql) To drop a column from a table, you use ALTER TABLE DROP COLUMN statement: ALTER TABLE table_name. (CAST(UPPER(. Aug 10, 2010 · Also, if your table has data in it then you can't add NOT NULL columns (and for some RDBMSs you can't add NOT NULL columns even when there is no data present in the table). What you could do to allow other roles to change tables and other database objects, is to grant these roles to the owner: This gives the role "my_user" the same (!) privileges as the role "owner_of_your_objects". I would like to run full-text search on the chem_name column. In this post All the forms of ALTER TABLE that act on a single table, except RENAME, SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into a list of multiple alterations to be applied together. 12345 would be an example of the above. Here is the PostgreSQL syntax: comment on column app_user_bookings. To add a column to an existing table, we have to use the ALTER TABLE statement. The ALTER TABLE statement is used to add, delete, or modify columns in an existing table. This can be used in much the same way Dec 31, 2013 · I would like to alter the table if the table has the column with same data type and number exists. edited Sep 28, 2023 at 6:42. Your statement should look like: ALTER TABLE core. For example, it is possible to add several columns and/or alter the type of several columns in a single command. Dec 8, 2017 · When a column is added with ADD COLUMN, all existing rows in the table are initialized with the column's default value ( NULL if no DEFAULT clause is specified). For example: TABLE: TAB. But when you tried: alter table x add column z text default 'some value'; then it took long time. Here is the how to add a unique constraint to your table in PostgreSQL 9. 1, compiled by Visual C++ build 1914, 64-bit on my Windows 2012 Server. Nov 21, 2018 · Comments are attached to a column using the comment statement: userid int not null, phonenumber int. Indexes and table constraints involving the column will be automatically dropped as well. ALTER COLUMN TYPE This form changes the Nov 1, 2012 · => ALTER TABLE test ALTER COLUMN x TYPE integer USING (trim(x)::integer); ALTER TABLE Thanks @muistooshort for adding the USING link. For a complete reference of all the data Feb 13, 2015 · 2. PostgreSQL supports the ALTER TABLE statement to modify the structure of the existing tables. scores drop constraint scores_gid_fkey, add constraint scores_gid_fkey foreign key (gid) references games(gid) on delete cascade; Jun 15, 2022 · When adding a new column you don't use SET DATA TYPE. You can also add a comment to the table: Additionally: int index is invalid. The new columns and their types are specified in the same style and with the the same restrictions as in CREATE TABLE. The query to do so is running like for ever. alter table public. Offending SQL: ALTER TABLE cliente ADD COLUMN topicos character varying(20)[]; * Login into our system requires a select from that very same table, so no one could login during the alter table. Hence, if you want to add multiple columns to a table, you need to execute ALTER TABLE command multiple times. 列关联的索引和表约束也将被自动删除掉。. The contents of the table after executing Oct 26, 2021 · Referencing the most recent docs, this operation can be done using two statements. A check constraint allows you to enforce data integrity rules at the database level. A check constraint uses a boolean expression to evaluate the values, ensuring that only valid data is inserted or updated in a table. Nov 2, 2011 · only 14000 rows, it doesn't seem like it should take that long. May 10, 2013 · If you want to make an existing (integer) column to work as a "serial", just create the sequence by hand (the name is arbitrary), set its current value to the maximum (or bigger) of your current address. Nov 10, 2010 · -- for each column specified: update my_table set my_column = 'f' where my_column is null; alter table my_table alter column my_column set default 'f'; alter table my_table alter column my_column set not null; ALTER TABLE my_table ADD COLUMN my_field boolean; ALTER TABLE my_table ALTER COLUMN my_field SET NOT NULL, ALTER COLUMN my_field SET DEFAULT false; The benefit of first is that you can calculate value for each row based on your row data (in other words you can refer fields). Jun 7, 2023 · By Admin June 7, 2023June 7, 2023. ALTERTABLE your_table_name action; As you can see, this statement’s syntax is fairly straightforward; however, the action part of the statement allows for a variety of options: ADD COLUMN — This allows us to add a new table column. ALTER TABLE table_name. DROP COLUMN [ IF EXISTS ] 这种形式从表中删除一个列。. end. This was because postgresql was actually rewriting You perform an instant DDL operation by using the clause ALGORITHM=INSTANT with the ALTER TABLE statement. The ALTER COLUMN form allows you to set or remove the default for the column. Otherwise it is created in the current schema. ALTER table can be used to. It is an essential skill for maintaining and updating a database as the structure evolves. I have been reading this article, which suggests the steps are as follows: Add a new tsvector column: ALTER TABLE frontend_chemical ADD COLUMN fts_document tsvector; Create a function to map the chem_name column to the document, and a Sep 10, 2019 · Shown below is the syntax for the PostgreSQL ALTER TABLE statement: 1. Mar 18, 2020 · I am trying to add a generated column to an existing table with this script. It only worked on tsql. From the fine manual: You must own the table to use ALTER TABLE. Our production environment just froze* this morning for a while when altering a table, adding a column actually. 285 then it will be 10. We use the following SQL statement: ALTER TABLE Persons. md5_hash VARCHAR(100) GENERATED ALWAYS AS. \d my_table. 3. You can always populate the new columns with data and modify the columns to be NOT NULL afterwards. The easiest way to accomplish this is to drop the constraint and re-add it with the desired parameters. The data type specifies what type of data the column can hold. answered Aug 30, 2022 at 13:00. Below is the syntax: Where: table_name is the name of the table to which you want to add a new column. Jan 4, 2024 · Altering or changing the structure of a table in PostgreSQL is a common task for database administrators and developers. Nov 16, 2009 · When one uses "ALTER TABLE tab ADD col", the new column gets added to the end of the table. COL_1 COL_2 COL_4. Jun 26, 2013 · 描述. 1. To add a new column to a table, you use ALTER TABLE ADD COLUMN statement: ALTER TABLE table_name. TABLE: TAB. You can add a new constraint with with alter table command. This PostgreSQL tutorial explains how to use the PostgreSQL ALTER TABLE statement to add a column, modify a column, drop a column, rename a column or rename a table (with syntax and examples). between the two data types json and jsonb. column_definition ：新列 Aug 29, 2013 · I have been able to alter my table and add a new column with these statements using them by themselves. Phúc Tĩnh. The SET DATA TYPE and TYPE are equivalent. Nov 4, 2020 · To make this a proper (recommended) identity column (Postgres 10 and later) you can do it like this: alter table the_table alter id set not null, alter id add generated always as identity; Now adding the identity attribute created a new sequence which we need to sync with the existing values in the column: select setval(pg_get_serial_sequence Jan 20, 2011 · Postgres: How to set column default value as another column value while altering the table 3 how-to modify a column type and set its default and current value in postgresql In this section, we are going to understand how the PostgreSQL ADD COLUMN Command is used to add one or more columns to the current database table. Aside: Why To add a column, use a command like: ALTER TABLE products ADD COLUMN description text; The new column is initially filled with whatever default value is given (null if you don't specify a DEFAULT clause). The ADD COLUMN form adds a new column to the table using the same syntax as CREATE TABLE. The ALTER TABLE statements add columns and change default All the forms of ALTER TABLE that act on a single table, except RENAME, SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into a list of multiple alterations to be applied together. To add a (multicolumn) unique constraint to a table: ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode); To add an automatically named primary key constraint to a table, noting that a table can only ever have one primary key: ALTER TABLE distributors ADD PRIMARY KEY (dist_id); To add a column to an existing table, we have to use the ALTER TABLE statement. How to add this column in every table at once ? Example – Add Column with a Default Value. or in decimal place we can use numeric also it will work. Now I want to add a new column (type boolean, nullable = false) without a default value. Sep 23, 2014 · SELECT 'ALTER TABLE ' + T. GRANT will not change this behavior, you must be the owner. TableName. If there is no DEFAULT clause, this is merely a metadata change and does not require any immediate update of the table's data; the added NULL values are supplied on readout, instead. Add or Drop constraint to column. Hot Network Questions First, specify the name of the table to which the column you want to change after the ALTER TABLE keywords. First drop the primary key constraint. Jan 4, 2024 · To remove a column from a PostgreSQL table the following syntax is used: ALTER TABLE table_name DROP COLUMN column_name; If you wanted to remove the ’email’ column from the ‘users’ table, the command would be: ALTER TABLE users DROP COLUMN email; Be aware that dropping a column will also remove all the data contained in that column, and To add a column, use a command like: ALTER TABLE products ADD COLUMN description text; The new column is initially filled with whatever default value is given (null if you don't specify a DEFAULT clause). Modify column datatype. with precession after decimal point 2 values it will come for example 10. Below is the basic syntax of adding a new column: ALTER TABLE table_name ADD COLUMN new_column_name data_type; where table_name is the name of the table to which you want to add the new column. Mar 14, 2013 · Debug, it may be Numeric (6,5) if the postgre sql errors out because it things the leading 0 is a decimal. 143 ms. column_name is the name of the new column you want to add. alter table tablename rename to oldtable; create table tablename (column defs go here); ### with all the constraints. To add a column at a specific position within a table row, use FIRST or AFTERcol_name. To add a column of type varchar to a table: ALTER TABLE distributors ADD COLUMN address varchar(30); That will cause all existing rows in the table to be filled with null values for the new column. ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NO INHERIT; You will have to replace constraint name as well as table name and content by your local requirements. I'm using PostgreSQL 12. 2. The syntax of the Alter add column command is given below: Aug 30, 2023 · To add a new column to an existing table in PostgreSQL, you can use the ALTER TABLE statement. BEGIN; ALTER TABLE t1 DROP CONSTRAINT Use ALTER TABLE ADD COLUMN statement to add a new column to existing table. Nov 20, 2009 · Can't add a comment to the appropriate place, but ALTER TABLE foo ALTER COLUMN bar TYPE new_enum_type USING bar::text::new_enum_type with a default on the column failed. In above statement, mytable is the name of the table you want to modify, column_name is the name of the column you want to make unique, and unique_column_name is a name you choose for the unique MySQL workbench img Right click at the table you want to alter and click alter table, then click Foreign Keys. And that is used in the constraint name. The table will be owned by the user issuing the command. 这种形式向表中增加一个新的列，列的说明语法和 CREATE TABLE 一样。. is_ms_shipped = 0 But it didn't work on PostgreSQL. I have a table with 500k elements. Now we want to add a column named "DateOfBirth" in the "Persons" table. If you want to create an index on a column, you do that using the create index statement: If you want an index over both columns use: You probably want to define the Aug 28, 2015 · create function addColumns () returns void as $$ begin for i in 1. The default is to add the Mar 7, 2023 · 6. However, to store decimal values at all, use numeric (precision, scale) or its synonym decimal (precision, scale) but notice that these are hard limits; according Aug 2, 2023 · To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_name ADD COLUMN new_column_name data_type constraint; In this syntax: First, specify the name of the table that you want to add a new column to after the ALTER TABLE keyword. As the IDENTITY has only been recently added, there were bugs affecting this particular command before Postgres 10. 12345 would need a field Numeric (6,5) 100. Jul 11, 2019 · You'll have to remove the default value first, then change the type, then add the new default value. But first find out the sequence: pg_get_serial_sequence. Second, provide the name of the column that you want to change the data type after the ALTER COLUMN clause. Jul 27, 2018 · and to set the default value: ALTER TABLE table ADD COLUMN col1 int default 0, Can't add column in pgAdmin4 and PostgreSQL 9. ALTER TABLE example2 RENAME example1fk TO example3fk; -- rename column In Postgres 9. But the column name will likely have to change in your example, too. case. x: CREATE UNIQUE INDEX constraint_name ON table_name (columns); Aug 2, 2023 · To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_name ADD COLUMN new_column_name data_type constraint; In this syntax: First, specify the name of the table that you want to add a new column to after the ALTER TABLE keyword. ADD COLUMN. Aug 2, 2023 · To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_name ADD COLUMN new_column_name data_type constraint; In this syntax: First, specify the name of the table that you want to add a new column to after the ALTER TABLE keyword. 2) can do check the existence of a column before add a new column? I don't want to create a function just for to check the existence. ColumnName NVARCHAR(100) Code for altering column if ColumnName with NVARCHAR and length 100 exists. In pgAdmin I can see the query is blocked by PID 0. Feb 25, 2018 · ALTER TABLE sourceTable ADD COLUMN ogc_fid int -- int or bigint or smallint GENERATED BY DEFAULT AS IDENTITY; Also be sure to use the latest point release. 23. IF EXISTS() BEGIN ALTER TABLE [dbo]. xxx_id_seq. DROP COLUMN column_name; Code language: SQL (Structured Query Language) (sql) When you remove a column from a table, PostgreSQL will automatically remove all of the indexes and constraints that involved the dropped column To add a column to an existing table, we have to use the ALTER TABLE statement. Yes, you can. Either provide a default value or allow the column to be NULLable. But if you have non-unique entries in your table, it will fail. So adding the column is actually done in a few milliseconds because Postgres only stores the information that a new column is available. 3 on my oldest and slowest machine: regression=# create table foo as select generate_series (1,14000) as x; SELECT. Original tTable structure is . You will need to say CASCADE if anything outside the table depends on the column, for example, foreign key references or views. ALTER TABLE my_table ALTER COLUMN description SET DEFAULT 'B2'. ADD COLUMN new_column_name data_type NOT NULL DEFAULT default_value; Let us create a column named attendance with default value of 84. 25. 要在选择的列之后添加新的列，我们可以使用 ALTER TABLE 语句。. INSERT INTO patient(col1) VALUES(10); INSERT INTO patient(col1) VALUES(15); you'll observe that you sucessfully made your column as an identity column Aug 30, 2023 · To add a new column to an existing table in PostgreSQL, you can use the ALTER TABLE statement. Description. ADD DateOfBirth date; Notice that the new column, "DateOfBirth", is of type date and is going to hold a date. Jan 24, 2014 · ALTER TABLE by default adds new columns at the end of the table. You can see Foreign Keys Options on the right side and just select cascade and click apply! answered Mar 10, 2022 at 8:49. Aug 30, 2023 · To add a new column to an existing table in PostgreSQL, you can use the ALTER TABLE statement. May 12, 2022 · An ALTER TABLE will never lock "the database", it will only lock the table. [TableName] ALTER COLUMN [ColumnName] NVARCHAR(200) [NULL|NOT All the forms of ALTER TABLE that act on a single table, except RENAME, SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into a list of multiple alterations to be applied together. Set or Remove default value to column. I am aware that using psql I can find these out individually but this is required to produce a result in a program I am writing to validate that a requested Dec 8, 2012 · alter table x add column z text; it was virtually instantaneous. Adds the column with the old default value. new_id column. Para adicionar uma nova coluna a um PostgreSQL tabela, o comando ALTER TABLE é usado com o seguintewing sintaxe: ALTER TABLE table-name. alter table Asset_Store add column. ALTER TABLE mn2012ct_geom2 ADD COLUMN obama_pct decimal(10,2) ALTER TABLE mn2012ct_geom2 ADD COLUMN romney_pct decimal(10,2) I was able to use this select statement produce the information I want it to in my terminal application. ALTER VIEW changes various auxiliary properties of a view. ADD new-column-name column-definition; O nome da tabela é o nome da tabela a ser modificada. . To add a new column to a table in PostgreSQL, you can use the ALTER TABLE statement with the ADD COLUMN clause. To set the value of your sequence see here. table will become. For syntax and usage details about instant DDL, see ALTER TABLE and Online DDL Operations in the MySQL documentation. May 24, 2016 · 0. We will use the alter table add column, command for adding the new column to an existing table. ALTER TABLE my_table ADD COLUMN description varchar(100) DEFAULT 'A1'; Modifies the column to use a different default value. Get a lock on table, add information about new column to system catalogs, and it's done. All the forms of ALTER TABLE that act on a single table, except RENAME, SET SCHEMA, ATTACH PARTITION, and DETACH PARTITION can be combined into a list of multiple alterations to be applied together. 10 loop alter table rflux add column tmp float; alter table rflux rename tmp to col||i; end loop; return; end; $$ language plpgsql; then do select * from addColumns (); but I get errors when renaming the column to col||i , or even just when I try i. To drop a column of a table, you use the DROP COLUMN clause in the ALTER TABLE statement as follows: ALTER TABLE table_name. COL_1 COL_2 COL_4 COL_3. If a schema name is given (for example, CREATE TABLE myschema. Reza S. Time: 482. and look under indexes for something like: "my_table_pkey" PRIMARY KEY, btree (datetime, uid) Drop it by doing: alter table my_table drop constraint my_table_pkey; Then create the new composite primary key by doing: Use ALTER TABLE ADD COLUMN statement to add a new column to existing table. A quick test with 8. Use ALTER TABLE ADD COLUMN statement to add a new column to existing table. ALTER TABLE TAB ADD COL_3. Just simply like this : ALTER TABLE IF NOT EXISTS table_name ADD COLUMN column_name data_type; Aug 2, 2023 · To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_name ADD COLUMN new_column_name data_type constraint; In this syntax: First, specify the name of the table that you want to add a new column to after the ALTER TABLE keyword. 12345 would need a field Numeric (8,5) When you write a select statement to see the decimals, it rounds to 2 In PostgreSQL, a CHECK constraint ensures that values in a column or a group of columns meet a specific condition. Jan 22, 2019 · Sample: ALTER TABLE schema. The RENAME clause causes the name of a table or column to change without changing any of the data contained in the affected table. – This form drops a column from a table. As per PostgreSQL documentation, you can select the minimum number for the floating point numbers using syntax float (n) where n is the minimum number of binary digits, up to 53. PostgreSQL ADD COLUMN command. new_column_name ：要添加的新列的名称。. I checked pg_stat_activity like 10 times and it never shows any queries locking the table: Jan 11, 2017 · To update comment, don't use alter command. 如果任何表之外的对象 Apr 15, 2015 · chem_name | character varying(200) | not null. Rename column. ALTER TABLE 变更一个现有表的定义。. Add column. All the forms of ALTER TABLE that act on a single table, except RENAME, and SET SCHEMA can be combined into a list of multiple alterations to applied together. 6. Feb 18, 2014 · Is postgresql (9. Note that defaults only apply to newly inserted rows. There is also further information on alter table add column statements here. 12345 would need a field Numeric (8,5) -100. Alternatively if you you just want to fill the column with initial data, you can drop the DEFAULT clause afterward Aug 23, 2015 · If data already exists in the column you should do: ALTER TABLE tbl_name ALTER COLUMN col_name TYPE integer USING (NULLIF(col_name, '')::integer); As pointed out by @nobu and @jonathan-porter in the comments to @derek-kromm's answer, somewhat cryptically. AFTER existing_column_name; table_name ：要修改的数据表的名称。. However as the naming of my example columns suggests I'd actually like the table to end up like this: Apr 7, 2016 · 56. insert into tablename (col1, col2, col3) select col1, col2, col3 from oldtable; To make a column unique in a PostgreSQL table, you can use the ALTER TABLE statement with the ADD CONSTRAINT clause. ( id serial PRIMARY KEY); ALTER TABLE barf ADD COLUMN scanned_in timestamp with time zone; BTW (just a hint): most of the ALTER syntax just mimics the syntax for CREATE TABLE (): the sub-syntax is mostly the same. PostgreSQL provides the ALTER TABLE statement to add, modify, or delete columns and constraints, rename tables, and more. mod is '1# mobile booking, 2# admin booking, 3# web booking, 4# tell call' It makes sense to add a check to prevent wrong values appearing: ALTER TABLE app_user_bookings ADD CHECK (mod IN (1,2,3,4)); In PostgreSQL, while adding a field it would be added at the end of the table. If we need to insert into particular position then. The postgres version is 9. Syntax: ALTER TABLE [schema_name. ]table_name. jv fu ve ov zq nq kr uq tn yn