SHOW STATS_HISTOGRAMS

你可以使用 SHOW STATS_HISTOGRAMS 语句查看通过 ANALYZE 语句 收集的直方图信息，该内容是数据库常规统计信息 的一部分。

语法图

ShowStatsHistogramsStmt

SHOW STATS_HISTOGRAMS - 图1

ShowLikeOrWhere

SHOW STATS_HISTOGRAMS - 图2

  1. ShowStatsHistogramsStmt ::=
  2.     "SHOW" "STATS_HISTOGRAMS" ShowLikeOrWhere?
  4. ShowLikeOrWhere ::=
  5.     "LIKE" SimpleExpr
  6. |   "WHERE" Expression

示例

  1. SHOW STATS_HISTOGRAMS;
  1. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  2. | Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
  3. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  4. | test    | t          |                | a           |        0 | 2020-05-25 19:20:00 |              7 |          0 |            1 |           1 |
  5. | test    | t2         |                | a           |        0 | 2020-05-25 19:20:01 |              6 |          0 |            8 |           0 |
  6. | test    | t2         |                | b           |        0 | 2020-05-25 19:20:01 |              6 |          0 |         1.67 |           1 |
  7. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  8. 3 rows in set (0.00 sec)
  1. SHOW STATS_HISTOGRAMS WHERE table_name = 't2';
  1. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  2. | Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
  3. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  4. | test    | t2         |                | b           |        0 | 2020-05-25 19:20:01 |              6 |          0 |         1.67 |           1 |
  5. | test    | t2         |                | a           |        0 | 2020-05-25 19:20:01 |              6 |          0 |            8 |           0 |
  6. +---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
  7. 2 rows in set (0.00 sec)

MySQL 兼容性

该语句是 TiDB 对 MySQL 语法的扩展。

另请参阅