![]() ![]() 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. This is similar to the switch statement in C. If no match is found, the result of the ELSE clause (or a null value) is returned. The following example truncates a TIMESTAMP value to hour date part: SELECT DATETRUNC('hour', TIMESTAMP ' 02:09:30') Code language: SQL (Structured Query Language. The datetrunc function returns a TIMESTAMP or an INTERVAL value. The parameter default is TIMESTAMPNTZ so. 1 I have a table with many timestamps in it, some of which may be null. ![]() 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. It could be an expression that evaluates to a timestamp or an interval. TOTIMESTAMP maps to one of the other timestamp functions, based on the TIMESTAMPTYPEMAPPING session parameter. There is a “ simple” form of CASE expression that is a variant of the general form above: 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. For formatting functions, refer to Section 9.8. The datetrunc function truncates a TIMESTAMP or an INTERVAL value based on a specified date part e.g., hour, week, or month and returns the truncated timestamp or interval with a level of precision. Table 9.32 illustrates the behaviors of the basic arithmetic operators ( +,, etc.). If the condition's result is not true, any subsequent WHEN clauses are examined in the same manner. Table 9.33 shows the available functions for date/time value processing, with details appearing in the following subsections. 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. To do that, use the coalesce function, which returns the first non-null. ![]() 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. Say youre looking at a PostgreSQL integer column where some rows are null. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |