在Sql Server中组合单个语句中的多个条件

Question

根据以下描述我必须CASE...END在SQL服务器中构建一个语句,帮助我构造一个复杂的CASE...END语句来满足以下条件.

if PAT_ENT.SCR_DT is not null and PAT_ENTRY.ELIGIBILITY is null then display display 'Favor'
if PAT_ENT.SCR_DT is not null and PAT_ENTRY.EL is equal to No, display 'Error'
if PAT_ENTRY.EL is Yes and DS.DES is equal to null or OFF, display 'Active'
if DS.DES is equal to N, display 'Early Term'
if DS.DES is equal to Y, display 'Complete'

提前致谢.

Answer 1

您可以将条件放在WHEN子句之后,如下所示:

SELECT
  CASE
    WHEN PAT_ENT.SCR_DT is not null and PAT_ENTRY.ELIGIBILITY is null THEN 'Favor'
    WHEN PAT_ENT.SCR_DT is not null and PAT_ENTRY.EL = 'No' THEN 'Error'
    WHEN PAT_ENTRY.EL = 'Yes' and ISNULL(DS.DES, 'OFF') = 'OFF' THEN 'Active'
    WHEN DS.DES = 'N' THEN 'Early Term'
    WHEN DS.DES = 'Y' THEN 'Complete'
  END
FROM
  ....

当然,可以说这样的复杂规则属于您的业务逻辑层,而不是数据库中的存储过程......