SHOW PLACEMENT LABELS
SHOW PLACEMENT LABELS 用于汇总可用于放置规则（Placement Rules）的标签及其对应的值。
语法
- ShowStmt
ShowStmt ::=
"SHOW" "PLACEMENT" "LABELS" ShowLikeOrWhere?
示例
SHOW PLACEMENT LABELS;
+--------+----------------+
| Key | Values |
+--------+----------------+
| region | ["us-east-1"] |
| zone | ["us-east-1a"] |
+--------+----------------+
2 rows in set (0.00 sec)
MySQL 兼容性
该语句是 TiDB 对 MySQL 语法的扩展。