Question

我有一个SQL查询，显示数据库中不同表的信息。其中一个字段称为PieceType，它包含PLT，CASE，CTN等值。每个公司可以有不同数量的PieceType，例如公司4可能只有PLT，但公司5可能有10种不同类型。我想在不同的列中显示这些类型，如：

Plt | CASE | CTN

我的SQL查询：

SELECT  c.Name,
        jp.PieceType
FROM customer c
LEFT JOIN job_new jn ON ja.JobID = jn.ID
LEFT JOIN job_pieces jp ON ja.JobID = jp.ID
WHERE c.Company_ID = compid
GROUP BY c.ID

现在查询只显示PieceTypes中的一个值，即使该公司可能有多个片段类型。我尝试了GROUP_CONCAT(DISTINCT jp.PieceType)，但显示了同一列中的所有值。我需要将每件作品放在一个单独的栏目中。样本数据库可以在sqlfiddle上找到：http://www.sqlfiddle.com/#!9/c34306/3

Answer 1

您可以选择在哪里查找所需的属性。

即：

Select 
name,
(select property from job_pieces where companyid = id and property = 'A') as A,
(select property from job_pieces where companyid = id and property = 'B') as B,
(select property from job_pieces where companyid = id and property = 'C') as C
 from company

Answer 2

我认为你正在寻找PIVOT TABLE。希望这有效：

SET group_concat_max_len=4294967294;
SET @COLUMNS = NULL;

/* Build columns to pivot */

SELECT GROUP_CONCAT(
        DISTINCT CONCAT(
            'CASE WHEN jp.PieceType = "', 
            jp.PieceType ,
            '" THEN 1 ELSE NULL END AS ',
            jp.PieceType
        )
) INTO @COLUMNS
FROM job_pieces jp;

/* Build full query */
SET @SQL = CONCAT(
        'SELECT  
                c.Name,
                ',@COLUMNS,'
        FROM customer c
        LEFT JOIN job_new jn ON ja.JobID = jn.ID
        LEFT JOIN job_pieces jp ON ja.JobID = jp.ID
        WHERE c.Company_ID = compid
        GROUP BY c.ID'
);

/* Prepare and execute the query*/
PREPARE stmt FROM @SQL;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

如何在Database中为值创建单独的列

2 个答案: