DO executes the expressions but does not return any results. In most cases,
DO is equivalent to
SELECT expr, ... that does not return a result.
In MySQL, a common use case is to execute stored procedure or trigger. Since TiDB does not provide stored procedure or trigger, this function has a limited use.
DoStmt ::= 'DO' ExpressionList ExpressionList ::= Expression ( ',' Expression )* Expression ::= ( singleAtIdentifier assignmentEq | 'NOT' | Expression ( logOr | 'XOR' | logAnd ) ) Expression | 'MATCH' '(' ColumnNameList ')' 'AGAINST' '(' BitExpr FulltextSearchModifierOpt ')' | PredicateExpr ( IsOrNotOp 'NULL' | CompareOp ( ( singleAtIdentifier assignmentEq )? PredicateExpr | AnyOrAll SubSelect ) )* ( IsOrNotOp ( trueKwd | falseKwd | 'UNKNOWN' ) )?
This SELECT statement pauses, but also produces a result set.
mysql> SELECT SLEEP(5); +----------+ | SLEEP(5) | +----------+ | 0 | +----------+ 1 row in set (5.00 sec)
DO, on the other hand, pauses without producing a result set.
mysql> DO SLEEP(5); Query OK, 0 rows affected (5.00 sec) mysql> DO SLEEP(1), SLEEP(1.5); Query OK, 0 rows affected (2.50 sec)
This statement is understood to be fully compatible with MySQL. Any compatibility differences should be reported via an issue on GitHub.