數據庫學習(day2)
1.SQL delete語法.
DELETE FROM?table_name
WHERE?some_column=some_value;
http://www.runoob.com/sql/sql-delete.html
2. 關于刪除的三個語句DROP/TRUNCATE/DELETE
DROP test;? ---刪除表test,并且釋放空間,test被完全刪除
TRUNCATE test;? ----刪除表test中的內容,并釋放空間,但不刪除表的定義,表的結構還在
DELETE FROM test WHERE age=30 AND country='us'; ---刪除指定數據
DELETE FROM test;?
DELETE * FROM test;--------僅刪除表內所有內容,保留表的定義,不釋放空間。
SQL SELECT TOP, LIMIT, ROWNUM | 菜鳥教程
SQL? SELECT TOP字句用法:
用于規定返回的記錄的數目
SQL Server/MS Access 語法
SELECT TOP number|percent column_name(s)
FROM table_name;
MySQL 語法
SELECT column_name(s)
FROM table_name
LIMIT number;
Oracle 語法
SELECT column_name(s)
FROM table_name;
WHERE ROWNUM <= number;