TRACE 语句用于查看具体 SQL 的执行情况。TRACE [SQL] 和 SHOW TRACE 要结合使用。

注意：TRACE SQL 和 EXPLAIN SQL 的区别在于 TRACE SQL 会实际执行该语句。

例如查看 select 1这条语句的执行情况。

mysql> trace select 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.03 sec)
mysql> show trace;
+------+----------+----------------+-----------------------------------+---------------+--------------------------+------+-----------+--------+
| ID   | TYPE     | GROUP_NAME     | DBKEY_NAME                        | TIME_COST(MS) | CONNECTION_TIME_COST(MS) | ROWS | STATEMENT | PARAMS |
+------+----------+----------------+-----------------------------------+---------------+--------------------------+------+-----------+--------+
|    0 | Optimize | DRDS           | DRDS                              | 3             | 0.00                     |    0 | select 1  | NULL   |
|    1 | Query    | TDDL5_00_GROUP | db218249098_sqa_zmf_tddl5_00_3309 | 7             | 0.15                     |    1 | select 1  | NULL   |
+------+----------+----------------+-----------------------------------+---------------+--------------------------+------+-----------+--------+
2 rows in set (0.01 sec)