# Analysis Of Implicit Data Type Conversion

+ Why does TiDB implicitly cast the**k** column instead of implicitly converting the number 1 to the right of the equal operator to the string '1'?


![left](./student-guide/diagram/01-14-1.png)

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You might ask, why does the database implicitly cast the k column in the example above instead of implicitly converting the number 1 to the right of the equal operator to the string '1'? Isn't it possible to use an index in that way, because there are many different strings that can be converted to the number 1, such as' 1 ',' 01 ', or' 1 ', etc.:

(omitted)

The database doesn't know which string to convert 1 to, so it doesn't implicitly convert a number to a string.