Question

我有这个 SQL 查询，其中我有一些 case 语句和计数，以便旋转我的“类 x”行，它返回类似这样的内容。

| Nombre Completo | Clase 1 | Clase 2|
--------------------------------------
| Example name   |   3      |    5   |
--------------------------------------

我需要的是替换数字，如果数字> 0，则将其替换为是，否则将其替换为否。我怎样才能做到这一点？ Mysql 查询：

SELECT  DISTINCT concat_ws(' ',U.firstname, U.lastname) as  Nombre_Completo,
COUNT(CASE WHEN b.name="Clase 1" THEN b.name END) Clase1,
COUNT(CASE WHEN b.name="Clase 2" THEN b.name END) Clase2,
COUNT(CASE WHEN b.name="Clase 3" THEN b.name END) Clase3,
COUNT(CASE WHEN b.name="Clase 4" THEN b.name END) Clase4,
COUNT(CASE WHEN b.name="Clase 5" THEN b.name END) Clase5,
COUNT(CASE WHEN b.name="Clase 6" THEN b.name END) Clase6,
COUNT(CASE WHEN b.name="Clase 7" THEN b.name END) Clase7,
COUNT(CASE WHEN b.name="Clase 8" THEN b.name END) Clase8,
COUNT(CASE WHEN b.name="Clase 9" THEN b.name END) Clase9,
COUNT(CASE WHEN b.name="Clase 10" THEN b.name END) Clase10,
COUNT(CASE WHEN b.name="Clase 11" THEN b.name END) Clase11,
COUNT(CASE WHEN b.name="Clase 12" THEN b.name END) Clase12
FROM mdl_logstore_standard_log as L
LEFT JOIN mdl_course as C ON L.courseid = C.id 
left JOIN mdl_user as U on L.userid = U.ID
JOIN mdl_bigbluebuttonbn AS b ON L.objectid = b.id
JOIN mdl_role_assignments AS ra ON L.userid = ra.userid
JOIN mdl_role AS r ON r.id = ra.roleid
WHERE (C.shortname LIKE '%CSG012020%') AND (ra.roleid=5)  AND (ra.roleid NOT IN (3,4))
GROUP BY Nombre_Completo;

Answer 1

使用IF()测试COUNT()的结果

SELECT  DISTINCT concat_ws(' ',U.firstname, U.lastname) as  Nombre_Completo,
IF(COUNT(CASE WHEN b.name="Clase 1" THEN b.name END) > 0, 'Yes', 'No') Clase1,
IF(COUNT(CASE WHEN b.name="Clase 2" THEN b.name END) > 0, 'Yes', 'No') Clase2,
IF(COUNT(CASE WHEN b.name="Clase 3" THEN b.name END) > 0, 'Yes', 'No') Clase3,
IF(COUNT(CASE WHEN b.name="Clase 4" THEN b.name END) > 0, 'Yes', 'No') Clase4,
IF(COUNT(CASE WHEN b.name="Clase 5" THEN b.name END) > 0, 'Yes', 'No') Clase5,
IF(COUNT(CASE WHEN b.name="Clase 6" THEN b.name END) > 0, 'Yes', 'No') Clase6,
IF(COUNT(CASE WHEN b.name="Clase 7" THEN b.name END) > 0, 'Yes', 'No') Clase7,
IF(COUNT(CASE WHEN b.name="Clase 8" THEN b.name END) > 0, 'Yes', 'No') Clase8,
IF(COUNT(CASE WHEN b.name="Clase 9" THEN b.name END) > 0, 'Yes', 'No') Clase9,
IF(COUNT(CASE WHEN b.name="Clase 10" THEN b.name END) > 0, 'Yes', 'No') Clase10,
IF(COUNT(CASE WHEN b.name="Clase 11" THEN b.name END) > 0, 'Yes', 'No') Clase11,
IF(COUNT(CASE WHEN b.name="Clase 12" THEN b.name END) > 0, 'Yes', 'No') Clase12
FROM mdl_logstore_standard_log as L
LEFT JOIN mdl_course as C ON L.courseid = C.id 
left JOIN mdl_user as U on L.userid = U.ID
JOIN mdl_bigbluebuttonbn AS b ON L.objectid = b.id
JOIN mdl_role_assignments AS ra ON L.userid = ra.userid
JOIN mdl_role AS r ON r.id = ra.roleid
WHERE (C.shortname LIKE '%CSG012020%') AND (ra.roleid=5)  AND (ra.roleid NOT IN (3,4))
GROUP BY Nombre_Completo;

Answer 2

每个：

COUNT(CASE WHEN b.name="Clase X" THEN b.name END)

在你的代码中可以写成：

SUM(b.name='Clase X')

因为 MySql 将 b.name='Clase 1' 之类的布尔表达式计算为 1 (true) 或 0 (false)。

此外，任何整数值都可以解释为 false，如果它是 0 或 true，如果它不同于 0。

所以你可以这样写你的查询：

SELECT concat_ws(' ', U.firstname, U.lastname) Nombre_Completo,
       CASE WHEN SUM(b.name='Clase 1') THEN 'yes' ELSE 'no' END Clase1,
       CASE WHEN SUM(b.name='Clase 2') THEN 'yes' ELSE 'no' END Clase2,
       CASE WHEN SUM(b.name='Clase 3') THEN 'yes' ELSE 'no' END Clase3,
       CASE WHEN SUM(b.name='Clase 4') THEN 'yes' ELSE 'no' END Clase4,
       CASE WHEN SUM(b.name='Clase 5') THEN 'yes' ELSE 'no' END Clase5,
       CASE WHEN SUM(b.name='Clase 6') THEN 'yes' ELSE 'no' END Clase6,
       CASE WHEN SUM(b.name='Clase 7') THEN 'yes' ELSE 'no' END Clase7,
       CASE WHEN SUM(b.name='Clase 8') THEN 'yes' ELSE 'no' END Clase8,
       CASE WHEN SUM(b.name='Clase 9') THEN 'yes' ELSE 'no' END Clase9,
       CASE WHEN SUM(b.name='Clase 10') THEN 'yes' ELSE 'no' END Clase10,
       CASE WHEN SUM(b.name='Clase 11') THEN 'yes' ELSE 'no' END Clase11,
       CASE WHEN SUM(b.name='Clase 12') THEN 'yes' ELSE 'no' END Clase12
FROM mdl_logstore_standard_log as L
LEFT JOIN mdl_course as C ON L.courseid = C.id 
left JOIN mdl_user as U on L.userid = U.ID
JOIN mdl_bigbluebuttonbn AS b ON L.objectid = b.id
JOIN mdl_role_assignments AS ra ON L.userid = ra.userid
JOIN mdl_role AS r ON r.id = ra.roleid
WHERE (C.shortname LIKE '%CSG012020%') AND (ra.roleid=5)  AND (ra.roleid NOT IN (3,4))
GROUP BY Nombre_Completo;

我删除了 DISTINCT，因为您 GROUP BY Nombre_Completo 后不需要它。

MySQL SQL 选择查询和替换值

2 个答案: