how to optimize sql query using execution plan

, found 1 matches left After the join standard row, no more rows are checked in the table for the previous row combination. Range checked for each record (Index map: #): MySQL did not find a good index to use, but found that if the column values from the previous table were known, some indexes might be available. The Using Filesort:mysql requires an additional pass to find out how rows are retrieved in sorted order, indicating that the

are checked in the table for the previous row combination. Range checked for each record (Index map: #): MySQL did not find a good index to use, but found that if the column values from the previous table were known, some indexes might be available. The Using Filesort:mysql requires an additional pass to find out how rows are retrieved in sorted order, indicating that the query needs to be optimized.

left join of the query, found 1 matches left After the join standard row, no more rows are checked in the table for the previous row combination. Range checked for each record (Index map: #): MySQL did not find a good index to use, but found that if the column values from the previous table were known, some indexes might be available. The Using Filesort:mysql requires an additional pass to find out how row

of the query, found 1 matches left After the join standard row, no more rows are checked in the table for the previous row combination. Range checked for each record (Index map: #): MySQL did not find a good index to use, but found that if the column values from the previous table were known, some indexes might be available. The Using Filesort:mysql requires an additional pass to find out how rows are retr

Label:Oracle-based application system many performance problems are caused by poor application SQL performance, so, SQL performance optimization is very important, analysis and optimization of SQL performance we generally look at the SQL implementation plan, this article on

after evaluating 80,000 combinations, it only evaluates 0.000006% of the possible groups.And perhaps no optimal connection sequence for this huge query. The best way to solve this problem in Oracle SQL is to manually specify the table connection sequence. To create the smallest solution set as soon as possible, the rule followed here is to combine tables. Generally, tables are connected

for a specific statement than index scan, we can instruct the optimizer to use full table scan. In Oracle, hints (prompt) is added to the statement to optimize the intervention optimizer. Hints is a mechanism provided by oracle to tell the optimizer to generate an execution plan as we tell it. We can use hints to implement: 1. Type of optimizer used 2. The optim

2. Table join(Table join) So far, we have been dealing with a single table. Let's look at the connections in the query. The following query gets the employee information and connects firstname and lastname, so that the returned information is more friendly. SELECT e.[Title], a.[City], c.[LastName] + ', ' + c.[FirstName] AS EmployeeNameFROM [HumanResources].[Employee] eJOIN [HumanResources].[Employee

How to intervene in the execution plan--Tips for using hints The cost-based optimizer is very intelligent. In most cases, it selects the correct optimizer, reducing the DBA burden. However, sometimes it is too clever to be confused. It chooses a poor execution plan, making

How Does oracle obtain the SQL Execution Plan of the client to optimize the SQL statement? Today is September 25,. I continue to learn about SQL optimization and have written two notes on how to obtain the

*. In terms of performance, it is not ideal to search for bookmarks. Because it will request additional I/O overhead to search in the field to return the required data rows. If you think that the bookmarked search does not affect the query performance, there are four options to avoid it: you can create a clustered index that will be used by the WHERE clause and take advantage of the index intersection, create a covered non-clustered index, or (if it

EXPLAINSELECT *, CAST (prorder. deliveryfeedbackaschar) asdeliveryfeedback, CAST (prorder. pocreatedateaschar) aspocreatedateFROM (SELECTrequest. fnumber, request. purtaskid, rd. request_detail_id, rd. request_id, item. skuid, item. sku, item. pur... mysqlselect optimizes the SQL execution plan EXPLAIN SELECT *, CAST(prorder.deliveryfeedback as cha

Today, we will discuss the execution plan of MSSQL to let everyone know how to view the optimization mechanism of MSSQL to optimize SQL queries, instead of simply using Program The execution result is optimized. -- Drop table

How to query the execution plan of an SQL statement in storage execution. The method is simple: first find the SQL statement in V $ sqlarea, then obtain SQL _id, and go to V $

performance, each of the items shown below is not ideal.Index or table scans ( indexed or sheet scan ) : may mean a better or extra index is needed.Bookmark Lookups ( Bookmark Lookup ) : Consider modifying the current clustered index, using the cover index, to limit the number of fields in the SELECT statement.Filter ( filtering ) : Remove any functions used in the WHERE clause, do not include views in SQL

1. Query the SELECT query statement execution plan using explainMysql> select * from baba where name = ' FJDSJF ';+------+--------+| ID | name |+------+--------+| 1 | FJDSJF |+------+--------+Query the

(add a space after select), execute and view the execution plan As a result, an execution plan is added, that is, the SQL Server considers two different SQL statements and establishes the

two different SQL statements and establishes the execution plan respectively; 4. Reuse the execution plan-using parameterized query methods 4.1 Non-parameterized SQLCopy codeThe Code i

* FROM Employee and view the execution plan We can see that this plan has been reused for 2 times; 3.3 modify SQL: SELECT * FROM Employee (add a space after SELECT), execute and view the execution plan As a result, an

By re-generating the execution plan, the execution plan deviation of Bound variables will be solved, resulting in the SQL Execution time being too long. The execution