PL/SQL 学习笔记3
SQL> var a number
SQL> begin
2 :a :=1000;
3 end;
4 /
PL/SQL procedure successfully completed.
SQL> edit
Wrote file afiedt.buf
1 begin
2 dbms_output.put_line(:a);
3* end;
SQL> /
通过这个代码可以看出通过pl/sql初始化赋值的Bind variable可以被其他Pl/sql程序调用
%type 类型应用的话 如果前面用的是database column的话 那么不可以加not null,前面引用的是声明的变量可以应用not null
A NOT NULLdatabase column constraint does not apply to variables that are declared using %TYPE.
Therefore, if you declare a variable using the %TYPEattribute that uses a database column defined as NOT
NULL, you can assign the NULLvalue to the variable.
eg:
绑定变量
A bind variable is a variable that you declare in a host environment.
Bind variables can be used to pass run-time values, either number or character, into or out of one or more PL/SQL programs. The PL/SQL
programs use bind variables as they would use any other variable. You can reference variables declared in the
host or calling environment in PL/SQL statements, unless the statement is in a procedure, function, or
package. This includes host language variables declared in precompiler programs, screen fields in Oracle Developer Forms applications, and iSQL*Plus bind variables.
绑定变量可以在主机环境下声明 可以在sqlplus 这种应用程序下声明 然后pl/sql程序来调用 调用需要在该变量前加colon
赋值的时候可以使用 exec :var_name := 10000; or begin :var_name := 1000 end; 或者是在PL/SQL中赋值
print(sqlplus command)可以打印出这个值
SQL> var result number
SQL> begin
2 select (sal*12) + nvl(comm,0)
3 into :result
4 from emp
5 where empno = 7369;
6 end;
7 /
PL/SQL procedure successfully completed.
SQL> print result
RESULT
------
9600
SQL> exec :result = 10000
BEGIN :result = 10000; END;
*
ERROR at line 1:
ORA-06550: line 1, column 15:
PLS
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机器情况
p4: 2.4
内存: 1 G
os: windows 2003
数据库: ms sql server 2000
目的: 查询性能测试,比较两种查询的性能
SQL查询效率 step by step
-- setp 1.
-- 建表
create table t_userinfo
(
userid int identity(1,1) primary key nonclustered,
nick&nbs ......
and exists (select * from sysobjects) //判断是否是MSSQL
and exists(select * from tableName) //判断某表是否存在..tableName为表名
and 1=(select @@VERSION) //MSSQL版本
And 1=(select db_name()) //当前数据库名
and 1=(select @@servername) //本地服务名
and 1=(select IS_SRVROLEMEMBER('sysadmin')) //� ......
SQL code动态sql语句基本语法
1 :普通SQL语句可以用Exec执行
eg: Select * from tableName
Exec('select * from tableName')
Exec sp_executesql N 'select * from tableName'
-- 请注意字符串前一定要加N
2:字段名，表名，数据库名之类作为变量时，必须用动态SQL
eg: declare @fname varchar(20)
......
declare @p int
declare @p1 int
declare @count int
set @p=0
set @p1=10
set @count=2
if(@count<>0 or @count<>1)
set @p=@p1*@count-10
SELECT [t1].[userid], [t1].[username], [t1].[userorder]
from (
SELECT ROW_NUMBER() OVER (ORDER BY [t0].[userorder]) AS [ROW_NU ......
有以下二张表：
政党表：政党ID，政党名称
议员表：议员ID，议员名称，政党ID
要求查询所有的政党信息，包含：政党名称，议员人数，并按议员人数的降序排列（不可以用子查询）。
正解:
SELECT a.name,
COUNT(b.id) AS counts
from zhen a
left join
yi b
on a.id=b.zhenid
GROUP ......
