问题就在于我们所插入的数据项中包含SQL关键字DROP TABLE,这两个关键字的意义是从数据库中清除一个表单。 而关键字之前的Robert');使得SQL执行器认为上一命令已经结束,从而使得危险指令DROP TABLE得到执行。 也就是说,这段包含DROP TABLE关键字的数据项使得原有的简单的插入姓名信息的SQL语句: 代码语言:javascript ...
Check constraints or partition function of source table ALTER TABLE with variable TableName ALTER vs UPDATE when creating a new column with default value. Alternate queries for MERGE Alternative for OR in WHERE clause Alternative for PIVOT Alternative of CURSOR in SQL to improve performance ?
1rowaffected(0.00sec)mysql>use lsz;//进入lsz数据库Database changed//创建lsztable表mysql>create tablelsztable(idint(10)notnull,namevarchar(100)notnull,age tinyint);QueryOK,0rowsaffected
With Duplicates as (select distinct a.custid as Customer_ID from customers2 a join customers2 b on a.custid <> b.custid and a.CustName = b.CustName and a.CustCity = b.CustCity and a.Passport_Number = b.Passport_Number ) Delete from Customers2 where custid in (select Customer_ID fr...
Table1 idname 1 Alice 2 Bob 3 Eve Table2 idvalue 1 100 1 200 2 300 SELECT DISTINCT * FROM Table1 #dist(t1)和t2的所有都选(仅限于t1有完全dup的rows),但是会出现duplicates INNER JOIN Table2 ON Table1.id = Table2.id; Result
1. NOT NULL in SQL The NOT NULL constraint in SQL is used to check and prevent you from providing NULL values in the columns. If the column has a NOT NULL constraint, then that table shouldn’t have NULL values or empty values in any of the rows. Why Do We Need to Use a NOT ...
You must also have space quota in the tablespace in which space is to be acquired in order to use the add_table_partition, modify_table_partition, move_table_partition, and split_table_partition clauses. Additional Prerequisites for Constraints and Triggers...
If multiple indexes are used in a single hint list, the duplicates are ignored, and the rest of the listed indexes are used to retrieve the rows of the table. The order of the indexes in the index hint is significant. A multiple index hint also enforces index ANDing, and the query opt...
00 sec) Records: 1 Duplicates: 0 Warnings: 0 使用set语句 语法格式: INSERT INTO 表名 SET 列名1=列值1, 列名2=列值2, ... 修改语句 修改单表记录 语法: UPDATE 表名称 SET 列名称=新值, 列名称=新值, ... WHERE 筛选条件 修改多表记录 语法: UPDATE 表1 AS 表1别名 INNER | LEFT | ...
CreateTable:CREATETABLE`test1` ( `id`int(6)DEFAULTNULL, `name`char(10)DEFAULTNULL ) ENGINE=InnoDBDEFAULTCHARSET=gbk #原字符集 rowinset(0.00 sec) mysql>altertabletest1converttocharactersetutf8; Query OK, 0rowsaffected (0.58 sec) Records: 0 Duplicates: 0 Warnings: 0 ...