A conditional expression, including scalar comparison conditions using, for example, any of the following comparison operators.
For more information about these operators, see SQL Functions, Operators, Expressions, and Predicates, B035-1145.
When a CHECK constraint is part of the column definition, then its defined search condition cannot reference any other columns in its table, nor are set specifications allowed. Valid column-level CHECK constraints that reference candidate keys of other tables are permitted. See also the CREATE TABLE topic “BETWEEN … AND … Constraints” in SQL Data Definition Language - Detailed Topics, B035-1184and Database Design, B035-1094.
A table-level CHECK constraint can compare any columns defined for its table, both against each other and against constant values.