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There is a setting you can alter called 'multi statement' that disables MySQL's 'safety mechanism' implemented to prevent (more than one) injection command. Typical to MySQL's 'brilliant' implementation, it also prevents user from doing efficient queries.
16 kwi 2016 · However, given how the conditions are re-used in your UPDATE statement, you could also take a different approach altogether: represent the affected IDs and the new values as a derived table and use an update with a join:
18 lut 2018 · You can use below one for one table if you want to update many columns of one table. UPDATE table SET col1 = CASE WHEN col3 = 'name1' THEN 'a' WHEN col3 = '2' THEN b ELSE 0 END , col2 = CASE WHEN col3 = '1' THEN 'b' WHEN col3 = 'name2' THEN 'c' ELSE '' END ;
For the multiple-table syntax, UPDATE updates rows in each table named in table_references that satisfy the conditions. Each matching row is updated once, even if it matches the conditions multiple times.
29 gru 2017 · You will need to write very complicated conditions if you want to update more than two rows. In such a case you can use INSERT ... ON DUPLICATE KEY UPDATE approach.
26 cze 2024 · Updating table rows using subqueries in MySQL enables precise modifications based on specific conditions or values from other tables. This technique leverages subqueries within the SET or WHERE clauses of the UPDATE statement, allowing dynamic and context-specific updates.
16 lut 2024 · In this article, we’ll learn the use of the CASE statement, IF() function, INSERT ... ON DUPLICATE KEY UPDATE clause and UPDATE with JOIN() function to update multiple columns in multiple rows with different values in MySQL.
