如何以我需要的方式获取mysql的输出如下

Question

我有一个表，其中一列有三个值a，b和c。 表的当前快照是

表名： - tblTest

值

tblColumn
a
a
a
b
b
b
b
c
c

我需要将输出完全视为

A B C
3 4 2

Answer 1

select sum(tblColumn = 'a') as A,
    sum(tblColumn = 'b') as B,
    sum(tblColumn = 'b') as C
from tblTest

SQL Fiddle Example

Answer 2

SELECT  SUM(CASE WHEN colName = 'a' THEN 1 ELSE 0 END) as A,
        SUM(CASE WHEN colName = 'b' THEN 1 ELSE 0 END) as B,
        SUM(CASE WHEN colName = 'c' THEN 1 ELSE 0 END) as C
FROM tableName

另一种技术是使用PreparedStatement，如果您有多个未知数量的值组，这是非常好的，例如，a,b,c,d,e,f,g,h,...

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'SUM(IF(tblColumn = ''',
      tblColumn,
      ''', 1, 0)) AS ',
      tblColumn 
    )
  ) INTO @sql
FROM
  Table1;
SET @sql = CONCAT('SELECT ', @sql, ' FROM Table1');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SQLFiddle Demo

Answer 3

试试这个

select tblColumn, Count(*) from tblTest group by tblColumn