You can use a label with iteration statements (FOR, LOOP, REPEAT and WHILE) and BEGIN … END compound statements in a stored procedure. The following rules apply:
If an ending label is specified, it must have a corresponding beginning label associated with that iteration or BEGIN … END statement. For example, an ending label following an END WHILE must have an equivalent beginning label and colon character preceding the corresponding WHILE.
This implies that if another iteration statement or compound statement is nested, the label name associated with the outer iteration or compound statement must not be used with any inner iteration statement(s) or compound statement(s).