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21 kwi 2012 · The initial case sets the field choice based on the selection and then I can set the field I need to match on for the join. A second case statement could be added for the right-hand side if the variable is needed to choose from different fields
MySQL CASE expression is a control flow structure that allows you to add if-else logic to a query. Generally speaking, you can use the CASE expression anywhere that allows a valid expression e.g., SELECT, WHERE and ORDER BY clauses. The CASE expression has two forms: simple CASE and searched CASE.
There is also a CASE operator, which differs from the CASE statement described here. See Section 14.5, “Flow Control Functions”. The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END.
18 wrz 1996 · A JOIN clause is used to combine rows from two or more tables, based on a related column between them. Let's look at a selection from the "Orders" table: OrderID
12 wrz 2018 · But a lot of times and in some more advanced and complex stuff like stored procedures, you’ll see SQL Case statement in places like Order by and/or SQL Where Case clause.
22 sie 2014 · SELECT conversation.c_id, conversation.user_one, conversation.user_two, users.name, users.lastName FROM `conversation` INNER JOIN `users` on users.id = CASE WHEN conversation.user_one = 1 THEN conversation.two WHEN conversation.user_two = 1 THEN conversation.user_one END WHERE `user_one` = 1 OR `user_two` = 1
17 maj 2023 · You can use a CASE expression in almost any part of a SQL statement, including the WHERE and JOIN. Given the example, the CASE expression performed better in this tutorial than the UNION ALL. However, this isn't an absolute rule.
