When a comparison (such as =) is performed between arguments with different data types, one or more arguments must be converted so that the comparison operation is done using one data type.

Some rules may lead to conversions that fail, or lead to unexpected results from the comparison. In these cases, you should explicitly convert one of the arguments using CAST or CONVERT.

You can override these conversion rules by explicitly casting arguments to another type. For example, if you want to compare a DATE and a CHAR as a CHAR, then you need to explicitly cast the DATE to a CHAR.

 See also