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28 Νοε 2014 · I am trying to write an SQL select statement where I need to change a condition (where clause) based on a CASE statement. Basically I am using a where clause. AND dep_dt <= trunc(SYSDATE) and I need to change <= to = if SYSDATE is a Monday. For all other days the operator will be <=.
Oracle CASE expression allows you to add if-else logic to SQL statements without having to call a procedure. The CASE expression evaluates a list of conditions and returns one of the multiple possible results. You can use a CASE expression in any statement or clause that accepts a valid expression.
In a simple CASE expression, Oracle Database searches for the first WHEN... THEN pair for which expr is equal to comparison_expr and returns return_expr. If none of the WHEN... THEN pairs meet this condition, and an ELSE clause exists, then Oracle returns else_expr. Otherwise, Oracle returns null.
EXISTS Condition. An EXISTS condition tests for existence of rows in a subquery. Description of the illustration exists_condition.eps. Table 6-11 shows the EXISTS condition.
In a simple CASE expression, Oracle Database searches for the first WHEN... THEN pair for which expr is equal to comparison_expr and returns return_expr. If none of the WHEN... THEN pairs meet this condition, and an ELSE clause exists, then Oracle returns else_expr. Otherwise, Oracle returns null.
The syntax for the CASE statement in Oracle/PLSQL is: CASE [ expression ] WHEN condition_1 THEN result_1 WHEN condition_2 THEN result_2 ... WHEN condition_n THEN result_n ELSE result END Parameters or Arguments expression Optional. It is the value that you are comparing to the list of conditions.
Oracle Database 23c extended CASE expressions in PL/SQL to support dangling predicates in simple CASE expression. These work like regular simple CASE expressions - you have a single selector. Each WHEN clause may contain a comparison condition and the right-hand side of the formula.
