| 标题 | oracle update数据更新的实现语句 |
| 范文 | oracle update数据更新的实现语句 SQL> -- create demo table SQL> create table Employee( 2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 / Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values ('01','Jason', 'Martin', to_date('19960725','YYYYMMDD'), to_date('20060725','YYYYMMDD'), 1234.56, 'Toronto', 'Programmer') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('02','Alison', 'Mathews', to_date('19760321','YYYYMMDD'), to_date('19860221','YYYYMMDD'), 6661.78, 'Vancouver','Tester') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('03','James', 'Smith', to_date('19781212','YYYYMMDD'), to_date('19900315','YYYYMMDD'), 6544.78, 'Vancouver','Tester') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('04','Celia', 'Rice', to_date('19821024','YYYYMMDD'), to_date('19990421','YYYYMMDD'), 2344.78, 'Vancouver','Manager') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('05','Robert', 'Black', to_date('19840115','YYYYMMDD'), to_date('19980808','YYYYMMDD'), 2334.78, 'Vancouver','Tester') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('06','Linda', 'Green', to_date('19870730','YYYYMMDD'), to_date('19960104','YYYYMMDD'), 4322.78,'New York', 'Tester') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('07','David', 'Larry', to_date('19901231','YYYYMMDD'), to_date('19980212','YYYYMMDD'), 7897.78,'New York', 'Manager') 3 / 1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description) 2 values('08','James', 'Cat', to_date('19960917','YYYYMMDD'), to_date('20020415','YYYYMMDD'), 1232.78,'Vancouver', 'Tester') 3 / 1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee 2 / ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION ---- ---------- ---------- --------- --------- ---------- ---------- --------------- 01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SQL> SQL> SQL> SQL> SQL> --Modify multiple rows with a single UPDATE statement; SQL> SQL> SQL> UPDATE Employee 2 SET City ='L.A.' 3 WHERE City = 'New York'; 2 rows updated. SQL> SQL> select * from employee; ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION ---- ---------- ---------- --------- --------- ---------- ---------- --------------- 01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 L.A. Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 L.A. Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 以下所列sql都是基于下表 create table test (name varchar2(30),code varchar2(10),i_d varchar2(10)); 插入数据 insert into test(name,code,i_d) values('zhu1','001','1'); insert into test(name,code,i_d) values('zhu2','002','2'); insert into test(name,code,i_d) values('zhu3','003','3'); commit; select * from test s; 1. update 更新i_d为1的数据 --方式1 update test set name='zhurhyme1', code='007' where i_d='1'; commit; 这样可以成功 --方式2 update test set (name,code)=( 'zhurhyme2','007') where i_d='1'; 注意,这样是不行，update set 必须为子查询，所以需要将其改为 : --方式3 update test set (name,code)=( select 'zhurhyme3','007' from dual) where i_d='1'; commit; 2.update 说完了，下面写一下关于for update，for update of 下面的资料是从网上找到的，可是具体的网址现在找不到了，请原谅小弟的粗心，引用人家的东东而不写出处. for update 经常用，而for updade of 却不常用，现在将这两个作一个区分 a. select * from test for update 锁定表的所有行，只能读不能写 b. select * from test where i_d = 1 for update 只锁定i_d=1的行,对于其他的表的其他行却不锁定 下面再创建一个表 create table t (dept_id varchar(10),dept_name varchar2(50)); c. select * from test a join t on a.i_d=t.dept_id for update; 这样则会锁定两张表的所有数据 d. select * from test a join t on a.i_d=t.dept_id where a.i_d=1 for update; 这样则会锁定满足条件的数据 e. select * from test a join t on a.i_d=t.dept_id where a.i_d=1 for update of a.i_d; 注意区分 d与e，e只分锁定表test中满足条件的数据行，而不会锁定表t中的数据，因为之前在procedure中作一个update，而需要update的数据需要关联查询，所以用了for update造成其他用户更新造成阻塞，所以才查到这段资料. for update of 是一个行级锁，这个行级锁，开始于一个cursor 打开时，而终止于事务的commit或rollback,而并非cursor的close. 如果有两个cursor对于表的同一行记录同时进行update，实际上只有一个cursor在执行，而另外一个一直在等待，直至另一个完成，它自己再执行.如果第一个cursor不能被很好的处理，第二个cursor也不主动释放资源，则死锁就此产生. 执行如下代码就会死锁(在两个command window中执行) declare cursor cur_test is select name,code from test where i_d=1 for update of name; begin for rec in cur_test loop update test set name='TTTT1' where current of cur_test; end loop; end; / declare cursor cur_test is select name,code from test where i_d=1 for update of name; begin for rec in cur_test loop update test set name='TTTT2' where current of cur_test; end loop; end; / 注意两个pl/sql块中没有commit; |
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