subquery

CriteriaBuilder cb = entityManager.getCriteriaBuilder(); CriteriaQuery<MemberAccountItem> cq = cb.createQuery(MemberAccountItem.class); Root<MemberAccountItem> root = cq.from(MemberAccountItem.class); cq.select(root); // 子查询 Subquery<Long&g

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First, the cascade of data, said: First we look at a chart of organizational structure This figure is a typical "tree structure", there is only one root node (King), under which a number of branch nodes, each node there are several sub-branch no

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Turn. mysql> UPDATE EACONTACTGROUPS A SET GROUPNAME = (SELECT CONCAT (B. GROUPNAME ,'-', A. GROUPNAME) FROM EACONTACTGROUPS B WHERE B. CORPID = A. CORPID AND B. USERID = A. USERID AND B. GROUPID = A. PARENTGROUPID) WHERE A. PARENTGROUPID IS NOT NULL;

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About select * from O1, O2 ...... As to why the database should be optimized, not repeat them here. Doing the project, how to maximize the efficiency of the sql query should be a topic we always: Here, the spirit of caution, simple manner, a little b

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REPLACE and INSERT operation is very similar. Only one exception, if the table for an old record with a PRIMARY KEY or a UNIQUE index to a new record has the same value, before the new record is inserted, the old record is deleted. See Section 13.2.4

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1, outer join · MS SQL SERVER table to support the connection between the two forms ① inherited from Sybase in the form of: Field 1 Field 2 *= (left join) Field 1 Field 2 =* (right connections) Without this form of full outer join syntax ② standard o

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1, the statement contains a subquery can try to connect the query may run faster; 2, for the Group by clause, if there are multiple packet dimensions, can be the only value in descending order of amount of data will improve query performance; 3, the

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in and exists in outer and inner tables is to make a hash join, but exists as a loop cycle is the appearance of each loop recycling internal table query. If two tables in a small, one large table, large table with a subquery exists, a small table wit

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Oracle Insert all three ways: First, the unconditional INSERT ALL Second, the conditions INSERT ALL Third, the conditions INSERT FIRST Insert ... Select Achieved using the Insert Select Insert to multiple table records 2007/06/25 First, the unconditi

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Fourth, the use of cursors in PL / SQL procedures for handling multi-line record of transactions often use a cursor to achieve. Cursor is a pointer to the context handle (handle) or a pointer. By the cursor, PL / SQL can control the context statement

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Keywords: mysql query optimizer (explain) Related Links: http://isky000.com/database/mysql-explain-detail explain sql statement is used to analyze and help optimize a command. explain the following syntax: explain [extended] select ... from ... where

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LONG columns can not appear in some parts of the SQL statement: 1, in the WHERE, GROUP BY, ORDER BY, CONNECT BY clause and a DISTINCT operation of the SELECT statement. 2, SQL functions (such as SUBSTR or INSTR) 3, expression or condition. 4, contain

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- Create a table for example using a subquery CREATE TABLE dept80 AS SELECT employee_id, last_name, salary * 12 annsal, hire_date FROM employees WHERE department_id = 80; SELECT * FROM employees; - ALTER TABLE statement - Use the ALTER TABLE statemen

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1 Statistics of the total number of records in a table: SELECT COUNT (1) / SUM (1) FROM tab; Explained: select 1 from table; and select anycol (the purpose of collection of any row in the table) from table; and select * from table is not from the eff

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DBA recently in a project the students asked a question: Why do so many slow query log shows Rows_examined: 0? Be noted that such statements are similar to the slow query select count (*) from (...) t; In explaining this, we first point out two relev

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Reference material 1 oracle on in and exists, not in and not exists http://blogold.chinaunix.net/u/32484/showart_270855.html 2 oracle exists and not exists in the Detailed description http://hi.baidu.com/qianyiliang/blog/item/54db82c2ca71fe1d0ef477a1

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1.explain query select statement is used to check the efficiency of the statements, we can optimize their own through the explain sql statement. After executing explain a few key fields, type: ref key: y Extra: Using where type: indicates the type of

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SQL-page statement Statement 1: select top 10 from user (select * from user where id not in (select top 10 id from user)) as t MySQL paging statement Statement 2: select * from user where userId not in (select u.userId from (select * from user limit

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oracle on in and exists, not in and not exists in and exists in outer and inner tables is to make a hash join, but exists as a loop cycle is the appearance of each loop recycling internal query the table. That exists has been efficient than in the st

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View definition and delete the SQL language 2008-11-05 19:23:42 Read 90 Comments 0 Word Count:. View from one or several basic table (or view) to export the table. It is different from the base table is a virtual table. Stored in the database view on

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explain sql statement is used to analyze and help optimize a command. explain the following syntax: explain [extended] select - from - where - If the extended, then explain in the statement executed, the query statement can show warnings correspondin

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For it is the oracle rownum is assigned to the system in order to return the rows from the query number, the distribution of the first row returned is 1, the second line is 2, and so on, the pseudo-field can be used to limit the query to return the t

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On the Web to see some of the points, in or not in the index are not used, sql optimization time yesterday and found that these views are not on the SELECT * FROM WF_DOC_GW_FAWEN F WHERE F.CFBT = 'ee' AND F.NDOCID IN (SELECT DISTINCT GI.SRC_NDOCID FR

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explain sql statement is used to analyze and help optimize a command. explain the following syntax: explain [extended] select ... from ... where ... If the extended, then explain in the statement executed, the query statement can show warnings corres

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In the construction of the table, try to meet the second Try not to include a subquery in the where; Queries on time, try not to write: where to_char (dif_date, 'yyyy-mm-dd') = to_char ('2007-07-01 ',' yyyy-mm-dd '); 2 in the filter, you can filter o

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Fifth, subquery When the results of a query is another query condition, known as sub-queries. Use subquery Note: Subqueries can be nested multi- Subquery requires parentheses () enclose Sub-query syntax: SELECT select_list FROM table WHERE expr opera

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2.1 General UPDATE statement If the data entered in the table there is an error, you can use the UPDATE statement to modify. Syntax is as follows: UPDATE table_name SET column = value [, column = value, ...] [WHERE condition]; Note: once you can upda

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XX views, sequences and synonyms 21.1 Views View from a table or more tables to export the virtual table, with a regular table except that it does not store data - it's just stored in a query definition. View with real tables, but also contains a ser

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Views, sequences, synonyms, indexes 1, A view from one or more tables to export the virtual table, with a regular table except that it does not store data - it's just a stored query in the definition of a real table with the same view, but also conta

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Subquery subquery concept: When the results of a query is another query condition, known as sub-queries. Use subquery Note: 1, the subquery can be nested multi- 2, sub-queries need parentheses () enclose the subquery syntax: SELECT select_list FROM t

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Views, sequences, synonyms, indexes 1 view View from a table or more tables to export the virtual table, with a regular table except that it does not store data - it's just a stored query in the definition of a real table with the same view, but also

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View 1) The view is from one or more tables in the export of the virtual table, with a regular table except that it does not store data - it's just a stored query in the definition of a real table with the same view, but also contains a series with t

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Subquery Subquery concept: When the results of a query is another query condition, known as sub-queries. Use subquery Note: Subqueries can be nested multi- Subquery requires parentheses () enclose Sub-query syntax: SELECT select_list FROM table WHERE

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Oracle's views, sequences, synonyms 1 view View from a table or more tables to export the virtual table, with a regular table except that it does not store data - it's just a stored query in the definition of a real table with the same view, but also

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oracle subquery (VI) Subquery concept: When the results of a query is another query condition, known as sub-queries. Use subquery Note: Subqueries can be nested multi- Subquery requires parentheses () enclose Sub-query syntax: SELECT select_list FROM

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LONG columns can not appear in some parts of the SQL statement: 1, in the WHERE, GROUP BY, ORDER BY, CONNECT BY clause and a DISTINCT operation of the SELECT statement. 2, SQL functions (such as SUBSTR or INSTR) 3, expression or condition. 4, contain

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Look at a nested query below: select * from person.StateProvince where CountryRegionCode in (select CountryRegionCode from person.CountryRegion where Name like 'C%') The above query uses a subquery. Although this SQL statement is not complicated, but

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Tested Mysql In clause can only put a subquery, then use the virtual table, the test can be used to record ~ ​​~ ~ begin create table tempTable1 as (select zpwas. `stock_id` from `zen_products_with_attributes_stock` as zpwas where zpwas. `products_id

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REPLACE and INSERT operation is very similar. With one exception, if the table for an old record with a PRIMARY KEY or a UNIQUE index to a new record has the same value, before the new record is inserted, the old record is deleted. Note that unless t

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In conditions of limited conditions, we can adjust the application's SQL Quality: 1 Do not be a full table scan (Full Table Scan): full table scan led to a large number of I / O 2 built and used as a good index: the index is a luxurious building, the

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The results of a query, the query as another parameter, that is, subquery 1 in the sub-query using aggregate functions <br /> query the table in the teachers than the average age of all teachers SELECT * FROM teacher WHERE age > (SELECT AVG(age)

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http://zmaze.org/?p=193 Basic Sql write notes Minimize the use of the IN operator, essentially all of the IN operator can use EXISTS instead. Do NOT IN operator, you can use NOT EXISTS or outer join + instead. IN subquery in the implementation of Ora

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Note: rownum starts at 1; 1.rownum record insertion in accordance with the order to sort the records, so there is order by the clause must be careful ah! (2) use rownum, order by primary key field is what effect? 3. Subquery rownum rn, and rn is used

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(1) select * from T1 where exists (select 1 from T2 where T1.a = T2.a); T1 and T2 small amount of data very large amount of data, T1 <<T2, (1) the query efficiency. (2) select * from T1 where T1.a in (select T2.a from T2); T1 and T2 data is very lar

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----------------------------------------------- Subquery - 1, single-row subquery - View the wages higher than the number for 7566 employees working in all employee information select * from emp where sal> (select sal from emp where empno = 7566); -

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-- Backup create table content_20110112 as select * from content; alter table content_20110112 add constraint content_20110112_key primary key(contid); -- Fall back update content t set t.products = (select o.products from content_20110112 o where o.

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Reference [switch] switch to a sql article about optimization Database and Design 2009-07-04 13:43:42 Read 10 Comments 0 Word Count: Subscribe Quote Xi Fengのdance of the [switch] switch to a article about optimizing sql We are in discussions on datab

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We are in discussions on database optimization stuff, just involved in the development of a data warehousing project, the following things be a little database optimization study + combat some of the feelings and experiences, and come up with to shar

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Introduced before taking a table of N records of a database of writing ... 1. ORACLE SELECT * FROM TABLE1 WHERE ROWNUM <= N 2. INFORMIX SELECT FIRST N * FROM TABLE1 3. DB2 SELECT * ROW_NUMBER () OVER (ORDER BY COL1 DESC) AS ROWNUM WHERE ROWNUM <= N

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Suppose the following table: A main table for the vote, a record for the voters - voter information table and the corresponding voting type of IP, so the actual connection is the result of our joint inquiry to which the table subject ~ 1: at right, o

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