和前2种的区别是do-while要先执行一次循环体,故do-while至少会执行一次循环体,for和while的循环体可能一次都不执行。 for语句的条件控制变量i为局部变量,for循环结束后就无法使用。while语句结束后,while的条件判断语句中的变量还可以继续使用,while的条件控制语句的变量不属于while循环结构。 死循环与跳转控制语句 实...
图2-3-3 5.Count the number of people in department 30 who receive a salary and the number of people who receive a commission (single statement). 语句: Select * from (select count(*) as both_comm_man from (select e.empno from emp2017303010 e where e.deptno = 30 and e.comm is not...
[:]退出 [ ( statement ) ] 可讓您使用 SELECT 陳述式的結果作為 sqlcmd 的傳回值。 如果為數值,最後一個結果資料列的第一個資料行會轉換成 4 位元組的整數 (long)。 MS-DOS、Linux 和 macOS 會將低位元組傳遞給父處理序或作業系統錯誤級別。 Windows 2000 和更新版本會傳遞完整的 4 位元組整數。 語法...
WHILE Loop Statement with Break and Continue The BREAK statement and CONTINUE statement are options to break the WHILE loop if there is a condition met and CONTINUE allows continuing with the iteration. They usually are used with IF logic. For this example, I will create a temporary table name...
BEGIN TRANSACTION; -- This SELECT statement will acquire an IS lock on the table. SELECT col1 FROM TestTable WITH (HOLDLOCK); 会话2: 事务启动,并且在此事务下运行的 SELECT 语句将获取共享锁 (S) 并将其保留在表中。 将获取所有分区的 S 锁,这将产生多个表锁,每个分区一个。 例如,...
<SELECT statement> ::= [WITH <common_table_expression> [,...n]] <query_expression> [ ORDER BY { order_by_expression | column_position [ ASC | DESC ] } [ ,...n ] ] [ COMPUTE { { AVG | COUNT | MAX | MIN | SUM } (expression )} [ ,...n ] [ BY expression [ ,...n...
Msg 13577, Level 16, State 1, Line 25 ALTER TABLE SWITCH statement failed on table 'MyDB.dbo.Staging_Department_2015_09_26' because target table has SYSTEM_TIME PERIOD while source table does not have it. 更新数据 使用常规的UPDATE语句更新当前表中的数据。 可...
BasicSELECTstatement基本的select语句 The basicsyntax for aSELECT statement is presented below. SELECT语句的基本语法如下。 |:多选一 []:可选择的内容 {}:多选一 没有被{}括起来的是必选 SELECT [DISTINCT |ALL] {* | select_list} FROM {table_name [alias] | view_name} ...
Learn the SQL SELECT statement to retrieve data from your database efficiently. Explore examples and syntax to master SQL queries.
SELECT 可以在×××或者日期类型的字段上做算术运算,日期类型只支持+ - 运算 SQL>selectename,sal,sal+300fromemp; 1. 运算符的优先级 跟数学中的概念一样,乘除优先于加减,可以使用括号改变优先级 示例四、 SQL>selectename,sal,sal*12+300fromemp;ENAME SAL SAL*12+300--- --- ---SMITH8009900ALLEN1600...