1、查询表中列数：
1) select count( column_name ) from user_tab_columns where table_name = '表名'; --表名为大写
eg : select count( column_name ) from user_tab_columns where table_name = 'OM_MAP';
2) select count( column_name ) from user_tab_columns where table_name = upper('表名');
eg : select count( column_name ) from user_tab_columns where table_name = upper('om_map'); --此处也就是将表名转换为为大写
2、查询表中所有列名：
1） SELECT COLUMN_NAME FROM USER_TAB_COLUMNS WHERE TABLE_NAME = '表名' ORDER BY COLUMN_ID; --表名为大写
eg : SELECT COLUMN_NAME FROM USER_TAB_COLUMNS WHERE TABLE_NAME = 'OM_MAP' ORDER BY COLUMN_ID;
2) SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = '表名' ORDER BY COLUMN_ID; --表名为大写
eg : SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = 'OM_MAP' ORDER BY COLUMN_ID;
3、查询表中所有列名，备注等：
1） SELECT t.table_name, t.colUMN_NAME, t.DATA_TYPE || '(' || t.DATA_LENGTH || ')', t1.COMMENTS FROM User_Tab_Cols t, User_Col_Comments t1 WHERE t.table_name = t1.table_name AND t.column_name = t1.column_name AND t.TABLE_NAME= '表名';
