In SP this can be 3 separate queries wrapped with external CASE: DELIMITER $$ ĬREATE PROCEDURE `case_in_where`(IN `column_selector` INT, IN `value` VARCHAR(255)) It’s similar to a nested IF-ELSE construct which is available in a lot of programming languages like Java, C, etc. The CASE expression has two forms: simple CASE and searched CASE. 14 You Could try the other format for the case statement CASE WHEN Product.typeid 10 THEN ( Select Statement ) ELSE ( Other select statement ) END FROM Product WHERE Product.productid pid See for more information. Generally speaking, you can use the CASE expression anywhere that allows a valid expression e.g., SELECT, WHERE and ORDER BY clauses. Because constant-evaluated condition for two of them will give false only one of 3 subqueries will be executed in practice. The MySQL CASE statement is a conditional construct and it returns values against a given condition being evaluated as true or false. MySQL CASE expression is a control flow structure that allows you to add if-else logic to a query. This tutorial explains the usage of MySQL IF and IF ELSE Statements in Select queries with syntax and practical programming examples: MySQL provides an IF () function which is a flow control function and depending on the condition specified and its evaluation to true or false, the rest of the statement executes. SELECT OrderID, Quantity, CASE WHEN Quantity > 30 THEN 'The quantity is greater than 30' WHEN Quantity 30 THEN 'The quantity is 30' ELSE 'The quantity is under 30' END AS QuantityText FROM OrderDetails Edit the SQL Statement, and click 'Run SQL' to see the result. To achieve highest performance use UNION ALL with 3 separate subqueries, one condition per subquery. for the right syntax to use near 'AS small, CASE (Amount > 0) I want my output like so Name Colour Small Large item1 red -35 item2 blue 48 etc.
SELECT t.name, t.colour, CASE WHEN (Amount < 0) AS small, CASE WHEN (Amount > 0) AS large FROM t Error.Let’s look at a practical example of a simple CASE statement.
WHENBut the condition built using logical operators cannot be optimized normally too. For example, you can use the CASE expression in clauses such as WHERE, ORDER BY, HAVING, SELECT and statements such as SELECT, UPDATE, and DELETE. 1 I am trying to use a select case statement on mysql DB. Before I go into details on how CASE works, take a look at the syntax of the CASE statement: CASE. Of course the construction which you show causes fullscan and cannot be optimized. SELECT (case when column1'A' then (select value from Table1) when column1'B' then (select value from Table2) when column1'C' then (select value from Table3) and so on uptil 35 more 'when' conditions. Usually the answers are that it should use AND, OR instead or Dynamic SQL.
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