sql语句，判断一个值是否在一个表中代码怎么写

Question

判断一个值是否在一个表中代码怎么写，代码加上些注释，怕看不懂

Answer 1

oracle语法
select * from A where not exists(select 1 from B where instr(',' || B.namelist || ',',a.name)>0;
sql语法
select * from A where not exists(select 1 from B where charindex(a.name,',' + B.namelist + ',')>0;