Question

我有这段代码：

SELECT DISTINCT
CASE
    WHEN abc > def THEN 'abc is larger than def'::text
    ELSE NULL::text
END AS case1,
CASE
    WHEN abc < ghi THEN 'def is larger than abc'::text
    ELSE NULL::text
END AS case2,
CASE 
    WHEN abc > jkl THEN 'abc is larger than jkl'::text
    ELSE NULL::text
END AS case3,

这看起来像这样：

-------------------------------------------------------------------------------------
|              case1          |           case2          |          case3           |
-------------------------------------------------------------------------------------
|    'abc is larger than def' | 'def is larger than abc' | 'abc is larger than jkl' |
-------------------------------------------------------------------------------------

我想要做的是创建一个名为'casesCombined'的列，而不是组合＆＃39;然后＆＃39;。例如，如果前2个案例为真，则列'casesCombined'将为'"abc is larger than def", "def is larger than abc"'。

像这样：

-----------------------------------------------------
|                  casesCombined                    |
-----------------------------------------------------
| 'abc is larger than def', 'def is larger than abc'|
-----------------------------------------------------

尝试了很多方法，但没弄清楚。我也不需要那些'case1'，'case2' ...

Answer 1

SELECT concat_ws(', ', CASE WHEN abc > def THEN 'abc is larger than def' END
                     , CASE WHEN abc < ghi THEN 'def is larger than abc' END
                     , CASE WHEN abc > jkl THEN 'abc is larger than jkl' END
                ) AS cases_combined
FROM tbl;

当没有CASE子句时，

ELSE默认为NULL concat_ws()忽略NULL值。

我没有添加额外的单引号，因为我假设你实际上并不想要结果中的那些。如果您这样做，只需添加：

Insert text with single quotes in PostgreSQL

将列复杂串联到一列中

1 个答案: