CASE WHEN pref_name in ('德岛', '香川', '爱媛', '高知') THEN '九州' WHEN pref_name in ...
现在,如果用户选择的值为NULL (从下拉列表中),则SQL查询将为如果用户选择的值是除NULL以外的任何值,则SQL查询将为我需要将这个条件放在Clause使用Case的位置,这样用户提供的任何输入都由SQL查询处理,并返回适当的结果。请指导如何将"ca 浏览7提问于2012-11-20得票数 0 1回答 case语句中的distinct条件 、 我有一...
CASE 陳述式有兩種類型: 簡式case 陳述式: 用來根據文字值輸入部分邏輯 搜尋的 case 陳述式: 用來根據表示式的值輸入部分邏輯 CASE 陳述式的 WHEN 子句定義當滿足時決定控制流程的值。 以下是具有含簡式 case-statement-when-clause 之 CASE 陳述式的 SQL 程序範例: CREATE PROCEDURE UPDATE_DEPT (IN p_workde...
Using CASE with the GROUP BY clause To apply aggregate functions, you can use the CASE statement in conjunction with the GROUP BY clause. Grouping with the CASE expression is a simple yet elegant method to arrange the query output in the required way. ...
SELECT Clause_1 INTERSECT SELECT Clause_2; MySQL中可以通过IN和子查询来间接实现INTERSECT的功能: SELECT col_1, col_2, col_3 FROM table_a AS a WHERE (a.col_1, a.col_2, a.col_3) IN (SELECT b.col_1, b.col_2, b.col_3 FROM table_b AS b); 4.3 EXCEPT/EXCEPT ALL EXCEPT对两个...
To express this logic in the WHERE clause, many people might code it like this: WHERE EmpID = CASE WHEN @ReturnAll<>1 THEN @EmpID ELSE EmpID END However, this is kind of counter-intuitive (why should we check that EmpID = EmpID ?) and can be really tough to implement when the condi...
Searched CASE expression: Evaluates, in the order specified, Boolean_expression for each WHEN clause. Returns result_expression of the first Boolean_expression that evaluates to TRUE. If no Boolean_expression evaluates to TRUE, the Database Engine returns the else_result_expression if an ELSE clause...
The CASE expression goes through conditions and returns a value when the first condition is met (like an if-then-else statement). So, once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in the ELSE clause. ...
The ELSE clause is a great way to catch bad or unexpected data values, and return a result other than NULL. Here are some things to consider when using the simple CASE expression: Allows only equality comparisons. Evaluates tests are evaluated in the order defined. ...
The SQL CASE statement is a control flow tool that allows you to add if-else logic to a query. Generally speaking, you can use the CASE statement anywhere that allows a valid expression – e.g. with the SELECT, WHERE, and GROUP BY clauses. Question: What is an SQL Case? In SQL, ...