SQL CREATE ALTER DROP TABLE: Difference between revisions

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=<tt>CREATE</tt>=
=<tt>CREATE</tt>=
<syntaxhighlight lang='sql'>
<syntaxhighlight lang='sql'>
CREATE TABLE person  
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] person  
( id smallint,  
( id smallint,  
   name varchar(30) NOT NULL,  
   name varchar(30) NOT NULL,  
   CONSTRAINT pk_person PRIMARY KEY (id)
   CONSTRAINT person_pkey PRIMARY KEY (id)
);
);
</syntaxhighlight>
</syntaxhighlight>
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|-
|-
|}
|}
If the <code>TEMPORARY</code> keyword is used, the created table will be [[SQL#Temporary_Table|temporary]] instead of [[SQL#Permanent_Table|permanent]].


=<tt>ALTER</tt>=
=<tt>ALTER</tt>=
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<syntaxhighlight lang='sql'>
<syntaxhighlight lang='sql'>
ALTER TABLE person ADD COLUMN birthday DATE;
ALTER TABLE person ADD COLUMN birthday DATE;
</syntaxhighlight>
<syntaxhighlight lang='sql'>
ALTER TABLE person DROP COLUMN birthday;
</syntaxhighlight>
</syntaxhighlight>
:{| class="wikitable" style="text-align: left;"
:{| class="wikitable" style="text-align: left;"
|-
|-
| [[PostgreSQL_DDL_Operations#Add/Remove_a_Column|PostgreSQL]] || [[MySQL_DDL_Operations#Alter_Table|MySQL]]
| [[PostgreSQL_DDL_Operations#Add/Remove_a_Column|PostgreSQL]] || [[MySQL_DDL_Operations#Alter_Table|MySQL]]
|-
|}
==Add/Remove a Constraint==
===<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>
:{| class="wikitable" style="text-align: left;"
|-
| [[PostgreSQL_DDL_Operations#NOT_NULL|PostgreSQL]] || [[MySQL_DDL_Operations|MySQL]]
|-
|}
===Primary Key===
<syntaxhighlight lang='sql'>
ALTER TABLE sometable ADD [CONSTRAINT sometable_pkey] PRIMARY KEY (somecolumn);
</syntaxhighlight>
If the name of the primary key constraint is not provided with the optional <code>CONSTRAINT ...</code>, the command will generate the name of the primary key constraint to match the <code><table_name>_pkey</code> pattern.
<syntaxhighlight lang='sql'>
ALTER TABLE sometable DROP CONSTRAINT [IF EXISTS] constraint_name [RESTRICT|CASCADE];
</syntaxhighlight>
:{| class="wikitable" style="text-align: left;"
|-
| [[PostgreSQL_DDL_Operations#Primary_Key|PostgreSQL]] || [[MySQL_DDL_Operations|MySQL]]
|-
|}
===Foreign Key===
<syntaxhighlight lang='sql'>
ALTER TABLE sometable ADD [CONSTRAINT sometable_someothertable_id_fkey] FOREIGN KEY (someothertable_id) REFERENCES someothertable(id);
</syntaxhighlight>
If the name of the constraint is not provided with <code>CONSTRAINT ...</code>, the command will generate the name of the foreign key constraint to match the <code><this_table_name>_<the_other_table_name>_<column_name>_fkey</code> pattern.
<syntaxhighlight lang='sql'>
ALTER TABLE sometable DROP CONSTRAINT [IF EXISTS] constraint_name [RESTRICT|CASCADE];
</syntaxhighlight>
:{| class="wikitable" style="text-align: left;"
|-
| [[PostgreSQL_DDL_Operations#Foregin_Key|PostgreSQL]] || [[MySQL_DDL_Operations|MySQL]]
|-
|-
|}
|}

Latest revision as of 14:32, 31 May 2024

Internal

Overview

CREATE

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] person 
( id smallint, 
  name varchar(30) NOT NULL, 
  CONSTRAINT person_pkey 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 [CONSTRAINT sometable_pkey] PRIMARY KEY (somecolumn);

If the name of the primary key constraint is not provided with the optional CONSTRAINT ..., the command will generate the name of the primary key constraint to match the <table_name>_pkey pattern. 

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

Foreign Key

ALTER TABLE sometable ADD [CONSTRAINT sometable_someothertable_id_fkey] FOREIGN KEY (someothertable_id) REFERENCES someothertable(id);

If the name of the constraint is not provided with CONSTRAINT ..., the command will generate the name of the foreign key constraint to match the <this_table_name>_<the_other_table_name>_<column_name>_fkey 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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