Search results
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.
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.
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. For the first syntax, case_value is an expression.
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.
INNER JOIN is used with an ON clause, CROSS JOIN is used otherwise. In general, parentheses can be ignored in join expressions containing only inner join operations. MySQL also supports nested joins. See Section 10.2.1.8, “Nested Join Optimization”.
7 mar 2019 · I'm working in a project with MySQL and using stored procedures to make my SELECT queries, so all of them have this same structure: BEGIN. SELECT * FROM `foo` WHERE . CASE. WHEN `column_selector` IS NULL THEN 1 . WHEN `column_selector` = 1 THEN `foo`.`column_1` = `value` WHEN `column_selector` = 2 THEN `foo`.`column_2` = `value` END.
