SQL CREATE ALTER DROP TABLE: Difference between revisions

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===Primary Key===
===Primary Key===
<syntaxhighlight lang='sql'>
ALTER TABLE sometable ADD PRIMARY KEY (somecolumn) <table_name>_pkey;
</syntaxhighlight>
The name of the primary key constraint is optional, and if not specified, it will be generated according to the <code><table_name>_pkey</code> pattern.
<syntaxhighlight lang='sql'>
ALTER TABLE sometable DROP CONSTRAINT [IF EXISTS] constraint_name [RESTRICT|CASCADE];
</syntaxhighlight>
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| [[PostgreSQL_DDL_Operations#PRIMARY_KEY|PostgreSQL]] || [[MySQL_DDL_Operations|MySQL]]
| [[PostgreSQL_DDL_Operations#Primary_Key|PostgreSQL]] || [[MySQL_DDL_Operations|MySQL]]
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Revision as of 19:35, 23 May 2024

Internal

Overview

CREATE

CREATE [TEMPORARY] TABLE person 
( id smallint, 
  name varchar(30) NOT NULL, 
  CONSTRAINT pk_person PRIMARY KEY (id)
);
PostgreSQL MySQL

If the TEMPORARY keyword is used, the created table will be temporary instead of permanent.

ALTER

ALTER TABLE person [...]

Add/Remove a Column

ALTER TABLE person ADD COLUMN birthday DATE;

ALTER TABLE person DROP COLUMN birthday;
PostgreSQL MySQL

Add/Remove a Constraint

NOT NULL

ALTER TABLE sometable ALTER COLUMN somecolumn SET NOT NULL;

ALTER TABLE sometable ALTER COLUMN somecolumn DROP NOT NULL;
PostgreSQL MySQL

Primary Key

ALTER TABLE sometable ADD PRIMARY KEY (somecolumn) <table_name>_pkey;

The name of the primary key constraint is optional, and if not specified, it will be generated according to the <table_name>_pkey pattern. 

ALTER TABLE sometable DROP CONSTRAINT [IF EXISTS] constraint_name [RESTRICT|CASCADE];
PostgreSQL MySQL

DROP

DROP TABLE person [...]
PostgreSQL MySQL

Features

AUTO_INCREMENT

AUTO_INCREMENT
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