SQL CREATE ALTER DROP TABLE: Difference between revisions

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==Add/Remove a Constraint==
==Add/Remove a Constraint==
===<tt>NOT NULL</tt>===
===<tt>NOT NULL</tt>===
<syntaxhighlight lang='sql'>
ALTER TABLE sometable ALTER COLUMN somecolumn SET NOT NULL;
</syntaxhighlight>
<syntaxhighlight lang='sql'>
ALTER TABLE sometable ALTER COLUMN somecolumn DROP NOT NULL;
</syntaxhighlight>
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:{| class="wikitable" style="text-align: left;"
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===Primary Key===
===<tt>PRIMARY KEY</tt>===
</syntaxhighlight>
:{| class="wikitable" style="text-align: left;"
:{| class="wikitable" style="text-align: left;"
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Revision as of 19:29, 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

PostgreSQL MySQL

DROP

DROP TABLE person [...]
PostgreSQL MySQL

Features

AUTO_INCREMENT

AUTO_INCREMENT
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