nested subquery

--Start Let's take a look at the definition of two tables: --User CREATE TABLE EMPLOYEE (USERID number (9,0) not NULL,---User ID companyid number (9,0),--- Company ID telno VARCHAR2 (a)---subscriber phone ); ALTER TABLE "EMPLOYEE" ADD CONSTRAINT "Pk_employee" PRIMARY KEY ("USERID"); --Company CREATE TABLE companies (CompanyID number (9,0) not NULL,---Corporate ID telno VARCHAR2 ()--- Company telephone ); ALTER TABLE "Company" ADD CONSTRAINT "Pk_company" PRIMARY KEY ("Compan

Oracle knowledge point Summary 3 (subquery) 1. Use of subquery 1. insert use of subquery when inserting data in insert, be sure not to add the Vaules keyword. SQL> create table copy_dep as select * from departments;Table created.SQL> truncate table copy_dep;Table truncated.SQL> insert into copy_dep 2 select * from departments;27 rows created. 2. When

Hello everyone, I encountered the following problem in the project: the example of using the combined primary key when the hibernate ing table is as follows: Product table: Item, the code for the primary key as the Union primary key ItemId is as follows: publicclassItemId {@ columnLongitemId; @ columnLonguserId;} @ Table (...) publicclassItem {@ Id Hello everyone, I encountered the following problem in the project: the example of using the combined primary key when the hibernate ing table is as

This article introduces four database query methods by combining text and text: Basic query, connection query, subquery, and regular expression query, for more information, see query data to obtain the required data from the database. Data query is the most common and important operation in database operations. You can use different query methods based on your data requirements. You can obtain different data through different query methods. MySQL uses

1. what is subquery and table join query? subquery: The select query statement is used in the select or where clause of the primary SQL statement; selectaname, (selectbnamefrombwherebidaid) fromawhereanamelika % table off 1. what is subquery and table join query: Subquery: The select statement is used in the select or

WHERE or HAVING search conditions. Searches all rows in the left table referenced by the left outer join and all rows in the right table referenced by the right outer join. CompleteAll rows of the two tables in the join operation are returned.5. subquery Use the select result of one query as the condition of another query Syntax: select * from Table 1 wher condition 1 (select .. from Table 2 where condition 2) 1. Integration with In select * from S

I am asked a question, the situation is as follows:He is going to update Divide_stat's New_amount field with the New_amount field based on Divide_act_channel_day.Conditions associated with two tables: Day=log_time,channel=channel--sql as follows:Update Divide_statSet divide_stat.new_amount= (select Divide_act_channel_day.new_amount from Divide_act_channel_daywhereDivide_stat.day=divide_act_channel_day.log_timeand Divide_stat.channel=divide_act_channel_day.channel);SQL Error: ORA-01427: single-li

Optimization of a complex subquery SQL statement and a complex subsql statement Select * from test. vmark vk where id in (select v. id from usr_center.vmark_degree_update_log v, (select min (id) id from usr_center.vmark_degree_update_log where degree_update_cause = 0 and degree_update_type = 0 group by user_id) log where v. id = log. id and v. degree_update_type = 0 and v. degree_update_before between '2017-01-01 00:00:00 'and'2017-01-10 00:00:00 ');+

Tags: structural elective course use name csdn and attribute contentContent from online:53090467The data of the main query is placed in the subquery for conditional validation, depending on the validation result (TRUE or FALSE) to determine whether the data results of the main query are retained.Here's an example of three tablesLet's start with the 3 datasheets that are used:Student Data Sheet: Sno School Number sname Ssex

Label:Source: Why not a subquery in SQL Server is not recommendedIn SQL Server, subqueries can be divided into correlated subqueries and unrelated subqueries, but not-in clauses are common for unrelated subqueries, but the not-in clause leads to the following two types of problems: Inaccurate results Poor query performance Let's take a look at why we try not to use the NOT in clause. The problem of inaccurate resultsIn SQL Server,

the results we need. However, we can also write this: Select customer_id, order_id from Table2 where customer_id to (select customer_id from table1 where city= ' Hangzhou '); Uh? What is the SELECT statement in the () bracket? The question is, what is the syntax and how can you accomplish the task, then this blog post revolves around this issue.What is a subquery? Simply put, subqueries are: As shown in the figure above, the

In Thinkphp, data is nested by classification and nested by thinkphp. In Thinkphp, data is nested by category. thinkphp nesting this article describes how to implement data nested by category in Thinkphp. Share it with you for your reference. The implementation method of data neste