inner-join

问题 I am trying to write a query that performs an inner join within an update statement. Here is the current query I am working with: UPDATE singulation1.`q096_cq33r08-ds01-n-testtable` SET visual = t2.visual, inspection_status = t2.inspection_status, inspector_name = t2.inspector_name FROM singulation1.`q096_cq33r08-ds01-n-testtable` t1 INNER JOIN singulation1.`q014_bq31t05-dw30-x` t2 ON (t1.print = t2.print AND t1.id3 = t2.id3); Something about MySql does not like the FROM clause. 回答1: For

问题 If I have one table that references the names of sponsors and the product ids of the products they recommend, as such: -------------------------------- |Name |Product ID 1|Product ID 2| -------------------------------- |Jon | 1 | 3 | |Sally| 1 | 2 | -------------------------------- And another table that lists the products: ---------------------------------------- |Product ID |Product Name|Product Price| ---------------------------------------- | 1 | Prod 1 | 25 | | 2 | Prod 2 | 35 | | 3 |

问题 EDIT: I will leave the post here as is, but what I really needed to accomplish needed to be reposted. I didn't explain the problem well enough. After trying again with quite a different starting point, I was able to get the query that I needed. That is explained here. ORIGINAL QUESTION: I'm having trouble. I have looked at similar threads, and I am unable to find a solution specific to this query. The database is very large, and group by seems to slow it down immensely. The problem is I am

问题 Here are how the dataframes columns look like. df1='device number', 'date', ....<<10 other columns>> 3500 records df2='device number', 'date', ....<<9 other columns>> 14,000 records In each data frame, neither 'device number', nor 'date' are unique. However, their combination is unique to identify a row. I am trying to form a new data frame which matches the rows from df1 and df2 where both device number and date are equal, and have all the columns from these df1 and df2. The pandas command I

问题 I’m using JPA 2.1, Hibernate 4.3.6.Final, and MySQL 5.5.37. How do I write a JPQL query that does a join? I’m trying below final String jpqlQuery = "SELECT m FROM Message m LEFT JOIN MessageReadDate mr " + " INNER JOIN m.group g " + " LEFT JOIN g.classroom c " + " LEFT JOIN c.ROSTER u WHERE " + " u.USER = :recipient AND " + " u.ENABLED = 1 AND " + " c.ENABLED = 1 AND " + " g.NAME = '' AND " + " m.author <> :author"; Query query = m_entityManager.createQuery(jpqlQuery); but getting the error

问题 I have a MySQL db with tables set up like this: Table1 Table2 ------ ------ id id, fk to Table1.id name name I want to update Table1 and set Table1.id = Table2.id if Table1.name = Table2.name . Or, in SQL: UPDATE table1 t1 INNER JOIN table2 t2 ON t1.name = t2.name SET t1.id = t2.id; How can I accomplish an equivalent statement using the SQLAlchemy Core API? I can call table1.join(table2, table1.c.name == table2.c.name) to create the join, but how can I update this joined table? 回答1: upd =

问题 Is there any difference between left join and inner join regarding performance? I use SQL Server 2012. 回答1: There is at least one case where LEFT [OUTER] JOIN is a better option than [INNER] JOIN . I talk about getting the same results using OUTER instead of INNER . Example (I am using AdventureWorks 2008 database): -- Some metadata infos SELECT fk.is_not_trusted, fk.name FROM sys.foreign_keys fk WHERE fk.parent_object_id=object_id('Sales.SalesOrderDetail'); GO CREATE VIEW View1 AS SELECT h

问题 Schema: create table TableA (A1 int) create table TableB (B1 int, B2 int) create table TableC (C1 int) Problematic query: SELECT * FROM TableA a INNER JOIN TableB b ON b.B1=a.A1 INNER JOIN (SELECT TOP 1 * FROM TableC c WHERE c.C1=b.B1 ORDER BY c.C1) d ON d.C2=b.B2 INNER JOIN OtherTable ON OtherTable.Foo=d.C1 Building this schema and running the query in SQLFiddle under SQL Server 2008 results in: The multi-part identifier "b.B1" could not be bound.: SELECT * FROM TableA a INNER JOIN TableB b

问题 Schema: create table TableA (A1 int) create table TableB (B1 int, B2 int) create table TableC (C1 int) Problematic query: SELECT * FROM TableA a INNER JOIN TableB b ON b.B1=a.A1 INNER JOIN (SELECT TOP 1 * FROM TableC c WHERE c.C1=b.B1 ORDER BY c.C1) d ON d.C2=b.B2 INNER JOIN OtherTable ON OtherTable.Foo=d.C1 Building this schema and running the query in SQLFiddle under SQL Server 2008 results in: The multi-part identifier "b.B1" could not be bound.: SELECT * FROM TableA a INNER JOIN TableB b

问题 Which of the following query is better... This is just an example, there are numerous situations, where I want the user name to be displayed instead of UserID Select EmailDate, B.EmployeeName as [UserName], EmailSubject from Trn_Misc_Email as A inner join Mst_Users as B on A.CreatedUserID = B.EmployeeLoginName or Select EmailDate, GetUserName(CreatedUserID) as [UserName], EmailSubject from Trn_Misc_Email If there is no performance benefit in using the First, I would prefer using the second...