select a.id,a.username,b.address from a left join b on a.id = b.A_id

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select a.id,a.username,b.address from t_user a left join t_address b on a.id = b.A_id

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原来是把不符合记录的也显示。那就用左外连接了

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select a.id,a.username,b.address from a left join b on a.id = b.A_id



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SQL code

select a.id,a.username,b.address from A a with (nolock)
left join B b with (nolock) on a.id=b.A_id

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select a.id,a.username,b.address from a , b where a.id = b.A_id(+);

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通用写法
select a.id,a.username,b.address from a left join b on a.id = b.A_id;

oracle 可以用
select a.id,a.username,b.address from a , b where a.id = b.A_id(+);


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select a.id,a.username,b.address from a left join b on a.id = b.A_id