Question

I m just confuse in this Query and i don’t know how to solve this if you have any idea about this please help me or helps are definitely appreciated

I have table structure like this and test column contain 3 value

UPDATE `test` SET test = test -3

when i execute this Query the result will be show like this

UPDATE `test` SET test = test -4

But when i execute this query the result will not proper save in test column like this

0 result required or i don’t need any subtract value also

Answer 1

Apparently you are using the BIGINT UNSIGNED data type. If you want to store negative numbers, you need to change it to a regular signed BIGINT (Also be sure to set it to NULL or NOT NULL as required):

ALTER TABLE test
  MODIFY COLUMN test BIGINT;

UPDATE: If you actually want to store 0 instead of -4 in your example, you can do so using the GREATEST() function like this:

UPDATE `test` SET test = GREATEST(CAST(test AS SIGNED) - 4,0)