如何简化多重转换MySql select语句？

Question

I am trying to perform a MySql select with many conditions, but want to perform a string comparison on a column that is an integer datatype. Is there a way to do this without having to cast the column to a varchar on every single condition within the where clause?

SELECT COUNT(*) 
FROM tablename 
WHERE CAST(col1 AS VARCHAR(10)) NOT LIKE '558%' 
  AND CAST(col1 AS VARCHAR(10)) NOT LIKE '566%' 
  AND CAST(col1 AS VARCHAR(10)) NOT LIKE '567%'
  AND CAST(col1 AS VARCHAR(10)) NOT LIKE '568%'
  AND CAST(col1 AS VARCHAR(10)) NOT LIKE '569%'
  AND CAST(col1 AS VARCHAR(10)) NOT LIKE '579%';

Before you ask why I'm not doing integer comparison: Instead of casting to a varchar, I could also just use plain integer comparison, but then I still would have to perform a math operation, ie col1/100000, for every item in the where clause, which leads to the same problem as to how can I simplify the statement?

Answer 1

You can use subquery:

SELECT COUNT(*)
FROM
( 
  SELECT CAST(col1 AS VARCHAR(10)) AS col1
  FROM tablename
) AS t
WHERE t.col1 NOT LIKE '558%'
...

Answer 2

The direct answer to your question is that casts are implicit in MySQL, so col1 NOT LIKE '556%' is equivalent to what you're doing.

It's always best to avoid using functions that reference column names in the WHERE clause, because that disables the use of indexes and requires every row in the table to be evaluated. I assume that you are aware of that, since you mentioned you would still "have to do a math operation."

If you actually know the scale of the number then a more correct query would be...

WHERE (col1 < 556 * 100000 OR col1 > 556 * 100000)
  AND ...

If that's logically correct based on what you are doing, then it's a better solution, because the optimizer will do that math only once, converting those into constants, rather than doing it once per row.

Also note that if you do know the scale of the numbers, then LIKE '556______' is also more logically valid than using % since _ matches exactly one character, where % matches zero or more.