Cloud computing learning roadmap materials, courseware, CASE search function grammar
In this article, we will show you the syntax of CASE search function:
CASE
WHEN Boolean_expression THEN
Result_expression [... n] [
ELSE
Else_result_expression
END
Parameter description:
The Boolean expression evaluated by WHEN Boolean_expression when it uses the CASE search format. Boolean_expression is an arbitrarily valid Boolean expression. The result type returns the highest precedence rule type from the type collection of result_expressions and optional else_result_expression. For more information, see prioritization of data types.
CASE search function: return result value introduction:
Evaluates the Boolean_expression of each WHEN clause in the specified order. Returns the result_expression of the first Boolean_expression whose value is TRUE.
If there is no Boolean_expression with the value TRUE, SQL Server will return else_result_expression; when the ELSE clause is specified. If no ELSE clause is specified, the NULL value will be returned.
Introduction of CASE WHEN examples 1. Select statements with only simple case
Select
CASE good_type
WHEN'0' THEN
'Food category'
WHEN'1' THEN
'Beverages'
WHEN'2' THEN
'Commodity'
WHEN'3' THEN
'fresh fruits'
END AS good_type_now
Good_type,user_id,user_name
FROM
Express.t_main_order
+-+
| | good_type_now | good_type | user_id | user_name | |
+-+
| | Food category | 0 | 1 | tina | |
| | Food category | 0 | 2 | tige | |
| | Beverage category | 1 | 3 | five |
| | Commodity | 2 | 4 | wate |
| | fresh fruits | 3 | 5 | fiww | |
| | fresh fruits | 3 | 6 | www | |
| | fresh fruits | 3 | 7 | wfiw | |
+-+
