A表左连B表，但又要A表中a1字段的值仅包含B表中 b1字段的记录，如何写SQL语句啊

select * from a,bwhere a.id=b.id(+) and instr(a1,b1)>0
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SQL code
select a.*  from a left join b    on a.a1 = b.b1 where b1 is not null;
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SQL code
select * from a,bwhere  a1 not in (select b1 from b where a.id=b.id(+))
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select a.*  from a left join b on a.a2 = b.b2 and a.a1<>b.b1