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1 lut 2010 · Here's a query to update a table based on a comparison of another table. If record is not found in tableB, it will update the "active" value to "n". If it's found, will set the value to NULL. UPDATE tableA LEFT JOIN tableB ON tableA.id = tableB.id SET active = IF(tableB.id IS NULL, 'n', NULL)"; Hope this helps someone else.
17 paź 2024 · MySQL provides two ways to insert a row into a table or update the row if it already exists. We can use the INSERT INTO … ON DUPLICATE KEY UPDATE syntax or the REPLACE 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. The WHERE clause specifies which record (s) that should be updated.
11 kwi 2019 · I need to do and IF/THEN statement in mysql based on whether a value exists in a column. If it exists, I need to perform an update on the record and if it does not, then an error should be thrown. I want to check that the siteID actually exists. How can I add an "IF EXISTS" statement?
29 kwi 2015 · IF EXISTS (select * from users where username = 'something') THEN. update users set id= 'some' where username = 'something'; ELSE. insert into users (username) values ('something'); END IF; end $$. delimiter ; and call it like this: call select_or_insert();
27 sty 2024 · In simple terms, UPSERT is the process of inserting a new record into a MySQL database table if the record does not exist or updating the existing record if it does. This operation is commonly required when you want to ensure that your dataset remains unique while still being able to update records as necessary.
22 sty 2018 · One simple answer is to use an integer created from the date as the unique key. Then you can use ON DUPLICATE KEY. This works fine for my purpose. INSERT INTO weatherbyday (wdID, DateTime, TempMin, TempMax,RainDay) . VALUES ('[YYYY][MM][DD]', '[YYYY]-[MM]-[DD] [hh]:[mm]:[ss]', '[th0temp-dmin]', '[th0temp-dmax]','[rain0total-daysum]')