那些遇到过的问题

如何查看mysql表中所有列的现有值的百分比？

dou*_*ack 5 mysql metadata

我有三个大表（每个表约 20 列），我想知道每列有多少行的值。

比如这张表：

ID   | TITLE               | SERVING     | NOTE
-------------------------------------------------------------------
6716 |  Yummy Molasses ... | 1 cookie    |
3765 |  Rosemary-Red Wi... |             |
5178 |  Stuffed Avocado... |             |
6025 |  Amazing Pea Sou... | about 1 cup |
4412 |  Overnight Oatme... | 1 cup       | Note: Steel-cut oats...
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可能会产生与此类似的结果：

ID   | TITLE               | SERVING     | NOTE
-------------------------------------------------------------------
100% | 100%                | 60%         | 20%
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这是一份内部报告，所以格式不是很重要。如果我只有count()百分比而不是百分比，那很好。有列名会很好，但不是必需的。等等。

我不太熟悉涉及更多元问题的查询，例如收集表名或处理表中的所有列，所以我很想看看人们的建议。

Rol*_*DBA 3

我有一个动态 SQL 解决方案

提出的查询

SET group_concat_max_len = 1048576;
SET @GivenDB = 'mydb';
SET @GivenTable = 'mytable';
SELECT CONCAT('SELECT ',GROUP_CONCAT(CONCAT('COUNT(',column_name,
')*100/COUNT(1) ',column_name,'_pct')),
' FROM ',table_schema,'.',table_name) sqlstmt
INTO @sql FROM information_schema.columns
WHERE table_schema=@GivenDB
AND table_name=@GivenTable;
PREPARE s FROM @sql; EXECUTE s; DEALLOCATE PREPARE s;
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例子

让我们使用我为另一个问题编写的示例表

mysql> use timyash
Database changed
mysql> show tables;
+-------------------+
| Tables_in_timyash |
+-------------------+
| mytable           |
+-------------------+
1 row in set (0.00 sec)

mysql> desc mytable;
+--------------+---------+------+-----+---------+----------------+
| Field        | Type    | Null | Key | Default | Extra          |
+--------------+---------+------+-----+---------+----------------+
| id           | int(11) | NO   | PRI | NULL    | auto_increment |
| transmitted  | int(11) | NO   |     | NULL    |                |
| connect_time | int(11) | NO   |     | NULL    |                |
+--------------+---------+------+-----+---------+----------------+
3 rows in set (0.02 sec)

mysql> select * from mytable;
+----+-------------+--------------+
| id | transmitted | connect_time |
+----+-------------+--------------+
|  1 |     2650131 |       117987 |
|  2 |     6465178 |        78073 |
|  3 |    25905117 |       159268 |
|  4 |    59178089 |       410282 |
|  5 |    73502942 |       596408 |
|  6 |    75695427 |       683045 |
|  7 |    77576167 |       740379 |
+----+-------------+--------------+
7 rows in set (0.00 sec)
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mysql>

显示建议的查询

mysql> SET group_concat_max_len = 1048576;
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenDB = 'timyash';
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenTable = 'mytable';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT CONCAT('SELECT ',GROUP_CONCAT(CONCAT('COUNT(',column_name,
    -> ')*100/COUNT(1) ',column_name,'_pct')),
    -> ' FROM ',table_schema,'.',table_name) sqlstmt
    -> INTO @sql FROM information_schema.columns
    -> WHERE table_schema=@GivenDB
    -> AND table_name=@GivenTable;
Query OK, 1 row affected (0.01 sec)

mysql> SELECT @sql\G
*************************** 1. row ***************************
@sql: SELECT COUNT(id)*100/COUNT(1) id_pct,COUNT(transmitted)*100/COUNT(1) transmitted_pct,COUNT(connect_time)*100/COUNT(1) connect_time_pct FROM timyash.mytable
1 row in set (0.00 sec)

mysql>
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已执行建议的查询

mysql> SET group_concat_max_len = 1048576;
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenDB = 'timyash';
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenTable = 'mytable';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT CONCAT('SELECT ',GROUP_CONCAT(CONCAT('COUNT(',column_name,
    -> ')*100/COUNT(1) ',column_name,'_pct')),
    -> ' FROM ',table_schema,'.',table_name) sqlstmt
    -> INTO @sql FROM information_schema.columns
    -> WHERE table_schema=@GivenDB
    -> AND table_name=@GivenTable;
Query OK, 1 row affected (0.02 sec)

mysql> PREPARE s FROM @sql; EXECUTE s; DEALLOCATE PREPARE s;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

+----------+-----------------+------------------+
| id_pct   | transmitted_pct | connect_time_pct |
+----------+-----------------+------------------+
| 100.0000 |        100.0000 |         100.0000 |
+----------+-----------------+------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql>
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使用空数据执行建议的查询

让我们将两行更改为具有 NULL 列数据

mysql> alter table mytable modify column connect_time INT NULL;
Query OK, 0 rows affected (0.66 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> update mytable set connect_time = 1/0 WHERE id in (2,5);
Query OK, 2 rows affected (0.06 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> select * from mytable;
+----+-------------+--------------+
| id | transmitted | connect_time |
+----+-------------+--------------+
|  1 |     2650131 |       117987 |
|  2 |     6465178 |         NULL |
|  3 |    25905117 |       159268 |
|  4 |    59178089 |       410282 |
|  5 |    73502942 |         NULL |
|  6 |    75695427 |       683045 |
|  7 |    77576167 |       740379 |
+----+-------------+--------------+
7 rows in set (0.00 sec)

mysql>
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让我们再次运行一下

mysql> SET group_concat_max_len = 1048576;
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenDB = 'timyash';
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenTable = 'mytable';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT CONCAT('SELECT ',GROUP_CONCAT(CONCAT('COUNT(',column_name,
    -> ')*100/COUNT(1) ',column_name,'_pct')),
    -> ' FROM ',table_schema,'.',table_name) sqlstmt
    -> INTO @sql FROM information_schema.columns
    -> WHERE table_schema=@GivenDB
    -> AND table_name=@GivenTable;
Query OK, 1 row affected (0.03 sec)

mysql> PREPARE s FROM @sql; EXECUTE s; DEALLOCATE PREPARE s;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

+----------+-----------------+------------------+
| id_pct   | transmitted_pct | connect_time_pct |
+----------+-----------------+------------------+
| 100.0000 |        100.0000 |          71.4286 |
+----------+-----------------+------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql>
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试一试 ！！！

更新时间 2014-12-29 15:25 美国东部时间

为了回应您的最新评论，请使用此版本

SET group_concat_max_len = 1048576;
SET @GivenDB = 'timyash';
SET @GivenTable = 'mytable';
SELECT CONCAT('SELECT ',
GROUP_CONCAT(CONCAT('SUM(IF(IFNULL(',column_name,
','''')='''',0,1))*100/COUNT(1) ',column_name,'_pct')),
' FROM ',table_schema,'.',table_name) sqlstmt
INTO @sql FROM information_schema.columns
WHERE table_schema=@GivenDB
AND table_name=@GivenTable;
SELECT @sql\G
PREPARE s FROM @sql; EXECUTE s; DEALLOCATE PREPARE s;
Run Code Online (Sandbox Code Playgroud)

您不需要使用此检查数据类型。

为了向您展示它的工作原理...

mysql> SET group_concat_max_len = 1048576;
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenDB = 'timyash';
Query OK, 0 rows affected (0.00 sec)

mysql> SET @GivenTable = 'mytable';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT CONCAT('SELECT ',
    -> GROUP_CONCAT(CONCAT('SUM(IF(IFNULL(',column_name,
    -> ','''')='''',0,1))*100/COUNT(1) ',column_name,'_pct')),
    -> ' FROM ',table_schema,'.',table_name) sqlstmt
    -> INTO @sql FROM information_schema.columns
    -> WHERE table_schema=@GivenDB
    -> AND table_name=@GivenTable;
Query OK, 1 row affected (0.03 sec)

mysql> SELECT @sql\G
*************************** 1. row ***************************
@sql: SELECT SUM(IF(IFNULL(id,'')='',0,1))*100/COUNT(1) id_pct,SUM(IF(IFNULL(transmitted,'')='',0,1))*100/COUNT(1) transmitted_pct,SUM(IF(IFNULL(connect_time,'')='',0,1))*100/COUNT(1) connect_time_pct FROM timyash.mytable
1 row in set (0.00 sec)

mysql> PREPARE s FROM @sql; EXECUTE s; DEALLOCATE PREPARE s;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

+----------+-----------------+------------------+
| id_pct   | transmitted_pct | connect_time_pct |
+----------+-----------------+------------------+
| 100.0000 |        100.0000 |          71.4286 |
+----------+-----------------+------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql>
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