Marek: Created page with "CREATE TABLE with a composite primary key

schema:scott

A composite key has more than one attribute (field). In this example we s..."

2012-07-12T15:04:04Z

Created page with "CREATE TABLE with a composite primary key <div class='ht'> <div class=params>schema:scott</div> <div> A composite key has more than one attribute (field). In this example we s..."

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CREATE TABLE with a composite primary key
<div class='ht'>
<div class=params>schema:scott</div>
<div>
A composite key has more than one attribute (field).
In this example we store details of tracks on albums - we need to
use three columns to get a unique key - each album may have
more than one disk - each disk will have tracks numbered 1, 2, 3...

The primary key must be different for each row of the table.
The primary key may not contain a null.
</div>
<source lang=sql class='tidy'>DROP TABLE track</source>
<source lang=sql class='setup'></source>

<source lang='sql' class='def'>CREATE TABLE track(
album CHAR(10),
disk INTEGER,
posn INTEGER,
song VARCHAR(255),
PRIMARY KEY (album, disk, posn)
)
</source>
<source lang='sql' class='def e-mysql e-sqlserver e-sybase e-db2'>CREATE TABLE track(
album CHAR(10) NOT NULL,
dsk INTEGER NOT NULL,
posn INTEGER NOT NULL,
song VARCHAR(255),
PRIMARY KEY (album, dsk, posn)
)
</source>
<div class="ecomm e-mysql e-sqlserver e-sybase e-db2" style="display: none">
We must explicitly state that the components are NOT NULL.
</div>
</div>
{{CREATE and DROP ref}}

Composite primary key - Revision history

Marek: Created page with "CREATE TABLE with a composite primary key schema:scott A composite key has more than one attribute (field). In this example we s..."

Marek: Created page with "CREATE TABLE with a composite primary key

schema:scott

A composite key has more than one attribute (field). In this example we s..."