Oracle的Cast的用法

轉自：https://blog.csdn.net/ziwen00/article/details/8685858  經常在前輩們的SQL中可以看到CAST,例如:   WITH T AS(SELECT LEVEL||' ' L FROM DUAL CONNECT BY LEVEL<=5), A(A,V) AS(SELECT CAST(L AS VARCHAR(30)),1 FROM T UNION

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