For example, this is a possible way of avoiding a division-by-zero failure: SELECT. The example above can be written using the simple CASE syntax: SELECT a,Ī CASE expression does not evaluate any subexpressions that are not needed to determine the result. This is similar to the switch statement in C. Syntax CASE WHEN THEN WHEN THEN .The CASE expression can be used with SELECT, WHERE, GROUP BY, and HAVING clauses. If no match is found, the result of the ELSE clause (or a null value) is returned. PostgreSQL supports CASE expression which is the same as if/else statements of other programming languages. ![]() such as MySQL and PostgreSQL, have their own syntax for creating conditional statements. The first expression is computed, then compared to each of the value expressions in the WHEN clauses until one is found that is equal to it. For example, if column a is declared as UNIQUE and contains the value 1, the following two statements have similar effect: INSERT INTO t1 (a,b,c) VALUES (1. Redshifts IF/THEN logic is a powerful tool for data analysis. There is a "simple" form of CASE expression that is a variant of the general form above: CASE expression The data types of all the result expressions must be convertible to a single output type. If the ELSE clause is omitted and no condition is true, the result is null. If no WHEN condition yields true, the value of the CASE expression is the result of the ELSE clause. If the condition's result is not true, any subsequent WHEN clauses are examined in the same manner. If the condition's result is true, the value of the CASE expression is the result that follows the condition, and the remainder of the CASE expression is not processed. Each condition is an expression that returns a boolean result. WHERE CASE WHEN x 0 THEN y/x > 1.The SQL CASE expression is a generic conditional expression, similar to if/else statements in other programming languages: CASE WHEN condition THEN resultĬASE clauses can be used wherever an expression is valid. For example, this is a possible way of avoiding a division-by-zero failure: CREATE OR REPLACE FUNCTION public. The example above can be written using the simple CASE syntax:Ī CASE expression does not evaluate any subexpressions that are not needed to determine the result. Otherwise, by default, the loop will execute the rest of. If no match is found, the result of the ELSE clause (or a null value) is returned. If you want to execute something specifically if the condition being tested is FALSE, you can use ELSE. The first expression is computed, then compared to each of the value expressions in the WHEN clauses until one is found that is equal to it. There is a â simpleâ form of CASE expression that is a variant of the general form above: ![]() ![]() The SQL CASE expression is a generic conditional expression, similar to if/else statements in other programming languages:ĬASE clauses can be used wherever an expression is valid.
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