【广告项目】mysql-select-if用法

mysql根据不同情况在一个字段显示不同值

SELECT
a.*, d2. NAME AS typeName,

IF (
a.position = '列车媒体',
d3.unit,
d4.unit
) AS suoshudanwei
FROM
ta_advertisement a
LEFT JOIN ta_dictionary_list d2 ON a.type = d2.id
LEFT JOIN ta_trainmedia t1 ON a.position_id = t1.id
LEFT JOIN ta_org_unit d3 ON t1.management_departmentId = d3.id
LEFT JOIN ta_stationmedia s1 ON a.position_id = s1.id
LEFT JOIN ta_org_unit d4 ON s1.companyId = d4.id
WHERE
a.delete1 = '1'

说明：若position为列车媒体，显示d3.unit的值赋给suoshudanwei,否则显示d4.unit的值赋给suoshudanwie

效果图：