Question

我有下表：

tableA
+-----------+--------+
| tableA_id |  code  |
+-----------+--------+
|         1 | code A |
|         2 | code B |
|         3 | code A |
|         3 | code C |
|         3 | code B |
|         4 | code A |
|         4 | code C |
|         4 | code B |
|         5 | code A |
|         5 | code C |
|         5 | code B |
+-----------+--------+

我想使用查询将代码A，代码B，代码C显示为列标题，然后值将显示tableA_id条目是否包含代码字段中的代码。所以像这样：

+-----------+------------------------------+
| tableA_id |  code A |  code B  |  code C |
+-----------+------------------------------+
|         1 |   yes   |          |         |
|         2 |         |   yes    |   yes   |
|         3 |   yes   |   yes    |   yes   |

etc...

你能在SQL中做到这一点吗？

Answer 1

使用condtitional聚合（在不同方言之间移植）：

SELECT tableA_id,
       MAX(CASE WHEN code ='code A' THEN 'yes' END) AS "code A",
       MAX(CASE WHEN code ='code B' THEN 'yes' END) AS "code B",
       MAX(CASE WHEN code ='code C' THEN 'yes' END) AS "code C"
FROM tableA
GROUP BY tableA_id;

的 SqlFiddleDemo_MySQL 的 SqlFiddleDemo_Postgresql

输出：

╔════════════╦═════════╦═════════╦════════╗ ║ tableA_id ║ code A ║ code B ║ code C ║ ╠════════════╬═════════╬═════════╬════════╣ ║ 1 ║ yes ║ (null) ║ (null) ║ ║ 2 ║ (null) ║ yes ║ (null) ║ ║ 3 ║ yes ║ yes ║ yes ║ ║ 4 ║ yes ║ yes ║ yes ║ ║ 5 ║ yes ║ yes ║ yes ║ ╚════════════╩═════════╩═════════╩════════╝

有很多可能性（搜索）：

PIVOT -> SQL Server/Oracle CROSSTAB -> Postgresql SELF OUTER JOIN -> All CONDITIONAL AGG -> All ...

Answer 2

在SQL语法

中你需要这样的东西

Select *
From Table1
pivot ( Aggregate function For Column Name in ([CodeA], [CodeB] , [CodeC])) as PivotTable

Answer 3

或者，如果您需要动态SQL语句，可以尝试以下方法。您只需要更改表和/或列的名称。

declare
cursor code is select code, rownum rn, count(*) over (partition by 1 ) as cnt from (select distinct code from test) order by 1;
build_Case clob;
a varchar2(100);
begin

for i in code loop
if i.rn <> i.cnt then
build_case := build_case || CHR(10) || ' max((case when code = ''' || i.code || ''' then ''yes'' else null end)) ' || i.code || ',';
else 
build_case := build_case || CHR(10) || ' max((case when code = ''' || i.code || ''' then ''yes'' else null end)) ' || i.code;
end if;
end loop;

build_case := 'select id,' || build_case || ' from test group by id';
dbms_output.put_line(build_Case);

--execute immediate build_Case;
end;
/

SQL将行值转换为列标题

3 个答案: