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不知何故,当我打电话时,我永远不会得到任何结果: select * from table_1 t1 where t1.c1 IS NOT NULL and trim(t1.c1) != '' ;
trim(t1.c1) != '' 部分导致问题实际上我什么也没返回。
Oracle 的奇特之处在于空字符串 ( '') 和NULL是一回事。就好像你在说:
''
NULL
trim(t1.c1) != NULL
这样的说法永远不会是真的。尝试:
trim(t1.c1) IS NOT NULL