The BOOLEAN data type stores 1-byte values that evaluate to true, false, or unknown. The actual values that you can insert into a BOOLEAN column (or use as Boolean literals) are as follows:

Accepted Values Meaning Return Value
true, t, y, yes, 1 True t
false, f, n, no, 0 False f
null Unknown null

Uppercase and lowercase values are accepted: TRUE or true, for example. Single quotes are required for all values except true, false, and null.