MySQL 正确的 Case 语句覆盖第一个声明的值

Question

我有这个案例陈述:

CASE 
WHEN CI.season = 1 THEN "Wet Season"
WHEN CI.season = 2 THEN "Early Wet Season"
WHEN CI.season = 3 THEN "Late Wet Season"
WHEN CI.season = 4 THEN "Dry Season"
WHEN CI.season = 4 and R.date_accessed > "2016-05-20 23:59:59" THEN "NULL"
ELSE "NULL" END as "Season" ,

如何表明如果季节值为 4 并且访问日期 > 则“2016-05-20 23:59:59”应等于 NULL。目前仅显示“旱季”。我认为它只读取了第一个场景。谢谢各位的回复。

Answer 1

试试这个:

CASE 
WHEN CI.season = 1 THEN "Wet Season"
WHEN CI.season = 2 THEN "Early Wet Season"
WHEN CI.season = 3 THEN "Late Wet Season"
WHEN CI.season = 4 and R.date_accessed > "2016-05-20 23:59:59" THEN "NULL"
WHEN CI.season = 4 THEN "Dry Season"
ELSE "NULL" END as "Season"

或者

CASE 
WHEN CI.season = 1 THEN "Wet Season"
WHEN CI.season = 2 THEN "Early Wet Season"
WHEN CI.season = 3 THEN "Late Wet Season"
WHEN CI.season = 4 THEN
    CASE WHEN R.date_accessed > "2016-05-20 23:59:59" THEN "NULL" ELSE "Dry Season" END
ELSE "NULL" END as "Season"