Restricting Row Retrieval with WHERE

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In a query, the WHERE clause specifies the data a row must (or must not) contain to be retrieved.

In singleton selects, where a query must only return one row, WHERE is mandatory unless a select procedure specified in the FROM clause returns only one row itself.

In SELECT statements within DECLARE CURSOR statements, the WHERE clause is optional. If the WHERE clause is omitted, a query returns all rows in the table. To retrieve a subset of rows in a table, a cursor declaration must include a WHERE clause.

The simple syntax for WHERE is:

WHERE <search_condition>

For example, the following simple WHERE clause tests a row to see if the
DEPARTMENT column is “Publications”:

WHERE DEPARTMENT = 'Publications'

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