A.SELECT DISTINCT 性別,AVG(年齡)FROM 學(xué)生 B.SELECT 性別,AVG(年齡)FROM 學(xué)生 ORDER BY 性別 C.SELECT 性別,AVG(年齡)FROM 學(xué)生 GROUP BY 性別 D.SELECT 性別,AVERAGE(年齡)FROM 學(xué)生 GROUP BY 性別
A.DROP FROM ST WHERE 性別="男" B.DROP FROM ST FOR 性別="男" C.DELETE FROM ST WHERE 性別="男" D.REMOVE FROM ST WHERE 性別="男"
A.字段有效性規(guī)則 B.記錄有效性規(guī)則 C.輸入掩碼 D.默認(rèn)值