The logical expressions sql_cond in the WHERE condition are similar to the general logical expressions for control statements. There are logical expressions with relational operators and other terms. Logical expressions can be linked to form an expression.
A single logical expression for a WHERE condition must always contain at least one column col from one of the database tables or views listed after FROM as an operand. You can specify the same column names (comp, dbtab~comp, tabalias~comp) for col as are listed in the specification of single columns after SELECT. You cannot specify aggregate expressions.