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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.
The MySQL CASE Statement. The CASE statement 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.
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.
26 sty 2024 · The CASE-WHEN statement in MySQL 8 is a robust tool for building dynamic and responsive SQL queries. Varying from basic conditional output to more complex evaluations involving subqueries and joins, CASE-WHEN can help you derive nuanced insights from your data in an elegant fashion.
18 gru 2014 · Use outer joins on both tables and move the CASE inside your COUNT: ft1.task, COUNT(case ft1.id when 1 then p1.id when 3 then u1.id end) as count. Non-hits for the CASE will give a null id and won't be counted. Note: Table a1 is in your where clause, but doesn't seem to be a selected table.
For the first syntax, case_value is an expression. This value is compared to the when_value expression in each WHEN clause until one of them is equal. When an equal when_value is found, the corresponding THEN clause statement_list executes. If no when_value is equal, the ELSE clause statement_list executes, if there is one.
