I've simulate your data example: mysql> SELECT * FROM `mail` I tested your function and it worked: mysql> SELECT removeExtraChar('abc - 123')
WHERE `subject` = removeExtraChar('abc - 123') Although you can remove some of the components manually, there is no command-line option for removing MySQL Workbench. If you used the function in the field subject if isnt indexed, this could take hours depending the amount of rows. I think that is your query the problem here. Note: I don't want to use extra mysql plugin. SELECT `id`,`user_id`,`subject` FROM `mail` where removeExtraChar(`subject`)=$subjectīut this goes in infinite loop. I tried with function CREATE FUNCTION `removeExtraChar`(`str` VARCHAR(255)) RETURNS varchar(255) CHARSET latin1 DELETE FROM tablename WHERE username IS NULL OR username '' It is advised to first do a SELECT query with same WHERE condition as that you are going to use in DELETE query to see which rows will be deleted: SELECT FROM. Still, I'm not entirely comfortable with this answer. The following SQL deletes the ContactName column from the Customers table: Example. I know what i write above is not available. If you want to delete all those rows containing username NULL AND where username is empty string ('') as well. Googling around, the popular answer seems to be 'just turn off safe mode': SET SQLSAFEUPDATES 0 DELETE FROM instructor WHERE salary BETWEEN 1300 SET SQLSAFEUPDATES 1 If I'm honest, I can't say I've ever made a habit of running in safe mode. The DROP COLUMN command is used to delete a column in an existing table. want to compare like following SELECT `id`,`user_id`,`subject` FROM `mail` where preg_replace('//', '',`subject`)=$subject
Is it possible to use preg_replace in my mysql query? WHERE condition is optional and is used to put a filter that restricts the number of rows affected by the DELETE syntax MySQL row query. DELETE FROM tablename tells MySQL server to remove rows from the table. Today, I tried to delete two tables from a database and upon trying I get the error message that a 'foreign key constraint fail' has occurred. That last bit is your answer.What i get value in php $subject = preg_replace('//', '', 'abc - 123') To delete a row in MySQL, the DELETE FROM statement is used: DELETE FROM tablename WHERE condition HERE.
#MYSQL DELETE COLUMN WORKBENCH UPDATE#
Here the result from the subquery in the FROM clause is stored as a temporary table, so the relevant rows in t have already been selected by the time the update to t takes place. ) Įxception: The preceding prohibition does not apply if you are using a subquery for the modified table in the FROM clause. The following forms: DELETE FROM t WHERE. For example, this limitation applies to statements of NN: As the Primary Key column does not store.
#MYSQL DELETE COLUMN WORKBENCH HOW TO#
In general, you cannot modify a table and select from the same table How to Create Alter and Drop Database table using MySQL Workbench PK: This will make the column Primary Key. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To. Quoting from the MySQL manual, Restrictions on Subqueries: In MySQL workbench, issue a simple delete all commands. So, your second query is closer to the mark, but hits another problem: MySQL applies a few restrictions to subqueries, and one of them is that you can't modify a table while selecting from it in a subquery. Still, I'm not entirely comfortable with this answer since it just assumes you should go change your database config every time you run into a problem. If I'm honest, I can't say I've ever made a habit of running in safe mode. Googling around, the popular answer seems to be "just turn off safe mode": SET SQL_SAFE_UPDATES = 0 ĭELETE FROM instructor WHERE salary BETWEEN 1300
0 kommentar(er)
