select t.dummy, decode(count('1'), null,0, 1) from dual t where 1 = 0 group by t.dummy;
select decode(count('1'), null,0, 1) from dual t where 1 = 0;
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请教两个查询
请教这两个查询的不同点,机制是什么? select t.dummy, decode(count('1'), null,0, 1) from dual t where 1 = 0 group by t.dummy; select decode(count('1'), null,0, 1) from dual t where 1 = 0;