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If data is NULL, then CONCAT() returns NULL (ignoring the second parameter), so the value does not change (updating a NULL value to be a NULL value), hence the 0 rows updated. In this case changing to the CONCAT_WS() function instead fixed the problem.
19 sty 2012 · I am sending an SQL UPDATE query, and the mySQL database is behaving strangely. It returns a successful response, but 0 rows are affected. The code is: Response: Successful 0 row(s) affected. ( Query took 0.0003 sec ) There is definitely a record with placeid='25' in the database.
The MySQL UPDATE Statement. The UPDATE statement is used to modify the existing records in a table. UPDATE Syntax. UPDATE table_name. SET column1 = value1, column2 = value2, ... WHERE condition; Note: Be careful when updating records in a table! Notice the . WHERE clause in the UPDATE statement.
First, specify the name of the table that you want to update data after the UPDATE keyword. Second, specify which column you want to update and the new value in the SET clause.
For example, if the table contains 1 and 2 in the id column and 1 is updated to 2 before 2 is updated to 3, an error occurs. To avoid this problem, add an ORDER BY clause to cause the rows with larger id values to be updated before those with smaller values: UPDATE t SET id = id + 1 ORDER BY id DESC;
15.1 Data Definition Statements. 15.1.1 Atomic Data Definition Statement Support. 15.1.2 ALTER DATABASE Statement. 15.1.3 ALTER EVENT Statement. 15.1.4 ALTER FUNCTION Statement. 15.1.5 ALTER INSTANCE Statement. 15.1.6 ALTER LOGFILE GROUP Statement. 15.1.7 ALTER PROCEDURE Statement. 15.1.8 ALTER SERVER Statement.
12 cze 2024 · The UPDATE statement in MySQL is essential for modifying existing data in a table. It’s commonly used to correct errors, update values, and make other necessary changes. This article explores the structure and use cases of the UPDATE statement, with clear and concise real-life examples.
