SQL_2

Oracle NOWAIT关键字的理解

sql_1:select1fromdualforupdate;sql_2:select1fromdualforupdate;sql_3:select1fromdualforupdatenowait;sql
hydeD·2023-04-01 08:47

python删除mysql表中数据

root",password="mysql",db="smy_db")cur=conn.cursor()sql_0="describestudent;"sql_1="select*fromstudent;"sql
ACE-Mayer·2022-04-14 07:22

SQL_2

Fig.11.selectcountrycode,avg(population)fromworld.citygroupbycountrycodehavingavg(population)>=100000;2.selectcountrycode,avg(population)fromworld.citywherepopulation>=100000groupbycountrycode;3.selec
艾马丫·2021-06-25 04:46

Oracle NOWAIT关键字的理解

sql_1:select1fromdualforupdate;sql_2:select1fromdualforupdate;sql_3:select1fromdualforupdatenowait;执行
wozeze1·2020-07-12 15:07

常用SQL_2

1.like//likeselectcount(*)fromim_messagewheremsglike"%你好%";2.deletedeletefromim_messagewheremsg="你好";3.groupbyselecta.user_idid,a.domain_usernamenamefromim_domain_userawherea.domain_id=5groupbyid;4.多表
陽_young·2020-02-20 04:42

数据库的事务隔离机制

SQL标准所定义的默认事务隔离级别是SERIALIZABLE，但是Oracle默认使用的是READCOMMITTED为避免出现第二类更新丢失sql_1:select1fromdualforupdate;sql
dreamsunday·2015-03-18 23:00

PHP与MySQL交互

"; //查询记录 $sql_2="select*fromtesttable"; $res_2=mysqli_query(
天子之骄·2015-02-23 17:00

mysql 分页查询语句优化

user_center.user_app_device数据量：8千万条分页语句SQL_1：SELECTid,uid,device_tokenFROMuser_app_deviceWHEREapp_id=100000000 LIMITi,100;分页语句SQL
u013399759·2014-11-19 14:00

delete from... not exisits

fromtable_name_aa wherea.column1='2013-12-0200:00:00' andnotexists(select*fromtable_name_bbwherea.id=b.a_id);sql
cuidiwhere·2014-02-19 22:00

mysql sql 索引相关用法，加快查询速度

适合大型级别的百级以上的数据分页：如果少于10W的用 sql_2/sql_3即可表1:create table `t1`(`id` int(11) not null auto_increment,`title
zhaowonq·2013-06-04 17:38

简单运用动态SQL定JOB整理表碎片SQL

declaresql_1varchar2(200);sql_2varchar2(200);beginsql_1:='altertabletestenablerowmovement';sql_2:='altertabletestshrinkspace
launch_225·2012-05-22 17:00

PL/SQL_2

1.游标类型    --定义一个游标类型 declare type emp_cursor is ref cursor; --定义一个游标变量 test_cursor emp_cursor; v_ename xxx.xxx%type; v_esal xxx.xxx%type; begin --执行 --把test_cursor和一个select结合
jackmeiowei·2010-09-28 00:00

SQL_2 - recursive queries, combined outer joins

select col1, cast(round(avg(col2),2) as decimal(9,2)) as aver_col2 from tab1 group by col1 order by col1 recursive query: with exp1 (col1, col2, col3) as ( -------- select top nodes  
luzl·2010-04-06 17:00
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