Sql Book
(Biswajit)
Search Conditions
This chapter discusses search condition clauses and the predicates used in them. The
following sections are presented:
? Search Condition
? BETWEEN Predicate
? Comparison Predicate
? EXISTS Predicate
? IN Predicate
? LIKE Predicate
? NULL Predicate
? Quantified Predicate
A search condition specifies criteria for choosing rows to select, update, delete, insert,
permit in a table, or fire rules on. Search conditions are parameters in the following
statements:
? In the SELECT statement, search conditions are used for two purposes as follows:
? In the WHERE clause, to determine rows to retrieve for further processing. The only
expressions not valid in this clause are aggregate functions and expressions
containing LONG columns that are not in long column functions.
? In the HAVING clause, to specify a test to apply to each group of rows surviving the
GROUP BY clause test(s). If a GROUP BY clause is not used, the test is applied to
all the rows meeting the WHERE clause conditions. References in a HAVING clause
to non-grouping columns must be from within aggregate functions. Grouping
columns can be referred to by name or with an aggregate function.
? In the UPDATE statement, search conditions in the WHERE clause identify rows that
qualify for updating.
? In the DELETE statement, search conditions in the WHERE clause identify rows that
qualify for deletion.
? In the INSERT statement, search conditions in the embedded SELECT statement
identify rows to copy from one or more tables or views into a table.
? In the DECLARE CURSOR statement, search conditions in the embedded SELECT
statement identify rows and columns to be processed with a cursor.
? In the CREATE VIEW statement, search conditions in the embedded SELECT statement
identify rows and columns that qualify for the view.
? In table CHECK constraints, the search condition identifies valid rows that a table may
contain.
? In rule firing conditions, search conditions identify conditions that cause rules to fire.
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