--
Script used to obtain the connection information of the SQL Server server (based on the original shard creation and writing)
Declare@ Dbname sysname,-- The name of the database to be queried (empty for all). The connection information of all databases is queried by default.@ Brief deip bit-- Whether to display the IP address (0 NO, 1 Yes). This control is added because the IP address query is time-consu
Solution for slow SQL query caused by custom functions, function SQL
During the report process, one report queries the exchange rate of the corresponding currency, and the exchange rate is in another table, the condition for querying the exchange rate is to query the exchange rate of the previous month of the statist
An additional column of serial numbers is automatically added to the SQL statement query results, and an SQL column is automatically added.
Sqlserver
It can be implemented using the row_number function.
As follows:
SELECT *, row_number () OVER (order by score (column name) DESC) AS rank FROM score
The SQL
expected results, change the query conditions, the sorting result becomes unrecognizable (the impact of the execution plan change).In a nutshell: No sorting is performed explicitly, and it is not expected that the query results will be sorted every time, even every time. Summarize: This article is based on two simple examples,From two aspects of execution planning and physical storage, "If
Distributed | data | database
/ * t-SQL code to implement distributed query of heterogeneous database using MS
exec sp_addlinkedserver ' ms_sql ', ', ' SQLOLEDB ', ' 172.18.9.20 'exec sp_addlinkedsrvlogin ' Ms_sql ', ' false ', NULL, ' Sa ', ' capec '/* Create a remote link for SQL Server to SQL Server database * *
ex
Http://www.cnblogs.com/dubing/archive/2011/12/09/2278090.htmlRecently the company has come to a very tiger DBA 10几 years of experience here is called Cai Teacher. Let us share the precious wealth that Cai Lao has brought to us, with the consent of our Chua. Welcome other DBAs to shoot bricks
Directory1. What is the execution plan? The execution plan is dependent on what information.2, unified SQL statement to reduce parsing overhead3. Reduce the
Directory1. What is the execution plan? The execution plan is dependent on what information.2, unified SQL statement to reduce parsing overhead3. Reduce the nesting of SQL statements4. Staging intermediate results using temporary table5. The OLTP system SQL statement must take a binding variable6. The spy problem of the bound variable of the tilted field7. Begin
table [table name] Add field name the datetime default function increases the date Type field, where the function can be now (), date (), and so on, representing the default value (which is most commonly used, and other properties, which can be referenced by the following data type Delete field: ALTER TABLE [table name] Drop field name Modify size of variable-length text field: ALTER TABLE [table name] ALTER field name varchar (N) Delete table: drop tables [table name] Nbsp;
First SQL statementSelect CompanyName GSMC,ZB Zhibiao from Left Join T_companycode on T_GSNDZB.GSBH=T_companycode.companyidQuery Result:A second SQL statementSELECT min(CompanyName) GSMC,cast(round(sum(T_xstj.hsje)/10000,2) asNumeric -,2)) Ndje fromT_xstj Left JoinT_companycode onT_companycode.companyid=T_XSTJ.GSBHwhere DateDiff( YearSjgetdate())=0 Group byGsbhQuery Result:Statements that are merged int
Id = % d of the SQL query statement in PHP (recommended), SQL % d
Some SQL statements are written as follows:
'Select id FROM dbname WHERE xx_id = % d; ', $ bl ['student _ id']
"Xx_id = % d", here % d Refers to a decimal number (d means decimal ), the content of the decimal number is the following $ bl ['student _ i
Directory1. What is an execution plan? The information on which the execution plan depends.2. Unify SQL statement writing to Reduce parsing overhead3. Reduce SQL statement nesting4. Use "temporary table" to save intermediate results5. The SQL statement of the OLTP system must use the bound variable.6. Preview the variable bound to the skewed field7. The
Read Catalogue
Begin
How SQL Server looks for records
SQL Server Join method
More specific execution procedures
Index statistics: The choice of the query plan is based on
Optimizing View Queries
Recommended Reading-MSDN Articles
For SQL Server optimizations, tuning queries can be a
Read SQL Server query planRead Catalogue
Begin
How SQL Server looks for records
SQL Server Join method
More specific execution procedures
Index statistics: The choice of the query plan is based on
Optimizing View Queries
Recommended Reading-M
Original: Set STATISTICS io and set STATISTICS time in SQL Server query performance optimizationIn recent times, has been exploring the SQL Server query performance issues, of course, also aimless search for a lot of information, but also from the online great God's articles learned a lot, here, to the great God salute
Enabling slow query log for tracking SQL Execution in MySQL and SQL log tracking in mysqlQuery slow query parametersShow variables like '% quer % ';
Slow_query_log (whether to record slow queries)
Slow_query_log_file (slow log file path)
Long_query_time (logs are recorded only when the specified time is
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