---4查询该用户下面所有表对应的数据字典SELECT COL.TABLE_NAME,       --COL.COLUMN_ID AS COLORDER,       TT.COMMENTS,       COL.COLUMN_NAME AS COLUMNNAME,       CASE         WHEN PKCOL.COLUMN_POSITION > 0 THEN          '√'         ELSE          ''       END AS ISPK,       COL.DATA_TYPE AS TYPENAME,       --DECODE(COL.DATA_TYPE, 'NUMBER', COL.DATA_PRECISION, COL.DATA_LENGTH) AS LENGTH,       COL.DATA_LENGTH    占用字节数,       COL.DATA_PRECISION AS PRECI,       COL.DATA_SCALE     AS SCALE,              CASE         WHEN COL.NULLABLE = 'Y' THEN          '√'         ELSE          ''       END AS CISNULL,              -- '' AS ISIDENTITY,              COL.DATA_DEFAULT AS DEFAULTVAL,       CCOM.COMMENTS    AS DETEXT /*,COL.NUM_DISTINCT AS NUM_DISTINCT*/  FROM USER_TAB_COLUMNS COL,       USER_COL_COMMENTS CCOM,       (SELECT AA.TABLE_NAME,               AA.INDEX_NAME,               AA.COLUMN_NAME,               AA.COLUMN_POSITION          FROM USER_IND_COLUMNS AA, USER_CONSTRAINTS BB         WHERE BB.CONSTRAINT_TYPE = 'P'           AND AA.TABLE_NAME = BB.TABLE_NAME           AND AA.INDEX_NAME = BB.CONSTRAINT_NAME        /*AND AA.TABLE_NAME IN ('AA')*/        ) PKCOL,       USER_TAB_COMMENTS TT WHERE COL.TABLE_NAME = CCOM.TABLE_NAME   AND COL.COLUMN_NAME = CCOM.COLUMN_NAME   AND COL.TABLE_NAME = TT.TABLE_NAME(+)      -- AND COL.TABLE_NAME = 'AA'   AND COL.COLUMN_NAME = PKCOL.COLUMN_NAME(+)   AND COL.TABLE_NAME = PKCOL.TABLE_NAME(+) ORDER BY COL.TABLE_NAME,col.column_id