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[Acronym] for __S__tructured __Q__uery __L__anguage.  Some DataBase professionals think the ''S'' should stand for "stupid."

[SQL] is a set-centric ProgrammingLanguage in which statements are excuted over a [Schema] of relations (tables), and return a table of results.

!! Syntax and examples

In this example, imagine we have a table called <tt>users</tt> which has an <tt>id</tt>, a <tt>name</tt> and an <tt>accesslevel</tt> column.

__Retrieving data:__

    <pre>
    SELECT ''col_1'', ''col_2'', ''col_n'' FROM ''table'' WHERE ''condition''
    </pre>

    Eg. to find the access level of user number 154:''''

        <pre>
        SELECT accesslevel FROM users WHERE id = 154;
        </pre>

__Inserting data:__

    <pre>
    INSERT INTO ''table'' (''column_one'', ''column_...'', ''column_n'') VALUES (''value_one'', ''value_...'', ''value_n'')
    </pre>

    Eg. to add a new user:''''

        <pre>
        INSERT INTO users (name, accesslevel) VALUES ('Craig', 10);
        </pre>

    The next available ID number is automatically assigned.

__Updating data:__

    <pre>
    UPDATE ''table'' SET ''column_one''=''value_one'', ''column_...''=''value_...'', ''column_n''=''value_n'' WHERE ''condition''
    </pre>

    Eg. to set an accesslevel of 15 to everyone whos name starts with a C:''''

        <pre>
        UPDATE users SET accesslevel=15 WHERE name LIKE 'C%';
        </pre>

__Removing data:__

    <pre>
    DELETE FROM ''table'' WHERE ''condition''
    </pre>

    Eg. to remove the user with ID number 30:''''

        <pre>
        DELETE FROM users WHERE id = 30;
        </pre>

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Part of CategoryProgrammingLanguages and CategorySpecialPurposeProgrammingLanguages

23 pages link to SQL:

Last edited on Tuesday, May 16, 2006 4:07:44 pm by AristotlePagaltzis

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