Question

我有一些SQL从正常的表中选择列。但是，我的一个列（u.cmc_rti_type）是一个数字，我希望它输出文本。我想我需要某种if语句。这是我的sql：

    SELECT '', s.student_number, s.lastfirst, s.grade_level, t.TEACHER, u.cmc_rti_tier, u.cmc_rti_type
            FROM students s 
            JOIN u_def_ext_students u
            ON u.studentsdcid = s.dcid
            LEFT JOIN cmc_homeroom_teacher t
            ON s.dcid = t.dcid
            WHERE u.cmc_rti_tier <> 0
            ORDER BY s.lastfirst

如果u.cmc_rti_type为1，那么我希望它输出'Reading' 如果u.cmc_rti_type为2，那么我希望它输出'Math' 如果u.cmc_rti_type为3，那么我希望它输出'Enrichment' 如果u.cmc_rti_type为4，那么我希望它输出'Both Math＆amp;读“

Answer 1

您可以在以下内容中使用CASE：

SELECT '', s.student_number, s.lastfirst, s.grade_level, t.TEACHER, u.cmc_rti_tier, 
        CASE u.cmc_rti_type WHEN 1 THEN 'Reading'
                            WHEN 2 THEN 'Math'
                            WHEN 3 THEN 'Enrichment'
                            WHEN 4 THEN 'Both Math & Reading'
        END AS Etc
        FROM students s 
        JOIN u_def_ext_students u
        ON u.studentsdcid = s.dcid
        LEFT JOIN cmc_homeroom_teacher t
        ON s.dcid = t.dcid
        WHERE u.cmc_rti_tier <> 0
        ORDER BY s.lastfirst

Answer 2

您可以使用CASE：

SELECT '', s.student_number, s.lastfirst, s.grade_level, t.TEACHER,
   u.cmc_rti_tier, 
   CASE u.cmc_rti_type 
      WHEN 1 THEN 'Reading'
      WHEN 2 THEN 'Math'
      WHEN 3 THEN 'Enrichment'
      WHEN 4 THEN 'Both Math & Reading'
      ELSE NULL
   END AS cmc_rti_type 
FROM students s 
JOIN u_def_ext_students u
  ON u.studentsdcid = s.dcid
LEFT JOIN cmc_homeroom_teacher t
  ON s.dcid = t.dcid
WHERE u.cmc_rti_tier <> 0
ORDER BY s.lastfirst

如果您使用 SQL Sever 2012 + ，则可以使用CHOOSE：

CHOOSE(u.cmc_rti_type, 'Reading', 'Math', 'Enrichment', 'Both Math & Reading') AS cmc_rti_type

的 LiveDemo

Answer 3

您需要case：

SELECT CASE u.cmc_rti_type 
            WHEN 1 then 'Reading'
            WHEN 2 then 'Math'
            WHEN 3 then 'Enrichment'
            WHEN 4 then 'Both Math & Reading' END, 
       s.student_number, 
       s.lastfirst, 
       s.grade_level, 
       t.TEACHER, 
       u.cmc_rti_tier, 
       u.cmc_rti_type
FROM students s 
JOIN u_def_ext_students u ON u.studentsdcid = s.dcid
LEFT JOIN cmc_homeroom_teacher t ON s.dcid = t.dcid
WHERE u.cmc_rti_tier <> 0
ORDER BY s.lastfirst

Answer 4

而且，对于完全不同的东西。

如果您具有必要的权限，则可以使用查找表来执行case语句的工作。这将允许您在将来添加更多选择，而无需查找执行此case语句的所有代码。

CREATE TABLE rti_type_lookup
(
 rti_type_value int not null,
 rti_type_label varchar(100) not null
)

INSERT INTO rti_type_lookup (rti_type_value, rti_type_label)
VALUES (1, 'Reading'),
       (2, 'Math'),
       (3, 'Enrichment'),
       (4, 'Both Math & Reading')

现在，当您需要获取文本版本时，您可以进行加入。而且，将来，您只需在rti_type_lookup表中添加新的查找值，而不是更新SELECT语句。

SELECT '', s.student_number, s.lastfirst, s.grade_level, t.TEACHER,
   u.cmc_rti_tier, rti_type_label AS cmc_rti_type 
FROM students s 
JOIN u_def_ext_students u
  ON u.studentsdcid = s.dcid
JOIN rti_type_lookup l
  ON u.cmc_rti_type = l.rti_type_value
LEFT JOIN cmc_homeroom_teacher t
  ON s.dcid = t.dcid
WHERE u.cmc_rti_tier <> 0
ORDER BY s.lastfirst

将SQL列结果转换为文本

4 个答案: