# 查看表的统计信息（C）
+ 查看列的元信息:
```7
mysql> SHOW STATS_HISTOGRAMS WHERE db_name = 'tpcc' AND table_name = 'orders';
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| tpcc    | orders     |                | idx_order   |        1 | 2021-09-13 11:12:05 |         156000 |          0 |            0 |           0 |
| tpcc    | orders     |                | PRIMARY     |        1 | 2021-09-13 11:12:04 |         156000 |          0 |            0 |           0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
2 rows in set (0.00 sec)
```
-------------------------------------------------------------
查看表的统计信息
查看表的各种统计信息
- 查看表的元信息                  SHOW STATS_META [ShowLikeOrWhere];
- 查看表的健康状态              SHOW STATS_HEALTHY [ShowLikeOrWhere];
- 查看列的元信息                 SHOW STATS_HISTOGRAMS [ShowLikeOrWhere];
查看直方图的信息             SHOW STATS_BUCKETS [ShowLikeOrWhere];
```
mysql> SHOW STATS_HISTOGRAMS WHERE db_name = 'tpcc' AND table_name = 'orders';
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| tpcc    | orders     |                | idx_order   |        1 | 2021-09-13 11:12:05 |         156000 |          0 |            0 |           0 |
| tpcc    | orders     |                | PRIMARY     |        1 | 2021-09-13 11:12:04 |         156000 |          0 |            0 |           0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
2 rows in set (0.00 sec)
```
- 可以通过 SHOW STATS_META 来查看表的总行数以及修改的行数等信息。
- 可以通过 SHOW STAT_HEALTHY 来查看统计信息的健康度，并粗滤估计表上的统计信息是否准确。当健康度低于刚才提到的自动更新阈值 tidb_auto_analyze_ratio，优化器会在窗口期内自动进行统计信息的收集操作
- 可以通过 SHOW STATS_HISTOGRAMS 来查看列的不同值数量以及 NULL 数量等信息。该语句会输出所有列的不同值数量及 NULL 的数量等信息。
- 可以通过 STAT_BUCKETS 来查看直方图的每个桶的信息。从该例中我们可以看到，不仅有表的直方图信息，还有索引的直方图信息。