sql两个查询语句如何做if判断链接起来

想做个判断，如果${layer3} == 集团总部 执行一段代码 否则执行另一段。 跨界转行，发现sql 的判断没有支持搜索的 求解详解！

SELECT ORG_ALIAS FROM ODS.HR_pt_structure_init
WHERE STRU_TREE_CODE LIKE 'lerthai-00001%' AND IN_USE=1 AND STRU_LEVEL=5 AND PARENT_STRU_ID IN 
(SELECT STRU_ID FROM ODS.HR_pt_structure_init WHERE STRU_TREE_CODE LIKE 'lerthai-00001%' AND IN_USE=1 AND STRU_LEVEL=4 AND ORG_ALIAS= ${layer3})
ORDER BY STRU_ORDER
------------------------------- 如果 ${layer3} == 集团总部 用下边的代码

SELECT ORG_ALIAS FROM ODS.HR_pt_structure_init
WHERE STRU_TREE_CODE LIKE 'lerthai-00001%' AND IN_USE=1 AND STRU_LEVEL=4 AND PARENT_STRU_ID IN 
(SELECT STRU_ID FROM ODS.HR_pt_structure_init WHERE STRU_TREE_CODE LIKE 'lerthai-00001%' AND IN_USE=1 AND STRU_LEVEL=3 AND ORG_ALIAS= ${layer3})
ORDER BY STRU_ORDER

在代码中可以加判断为啥非得用sql
你要是用mybatis的话可以用if test