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field Assuming that a relationship satisfies 1NF and that other columns other than the primary key depend on the primary key, the second normal form (2NF) is satisfied. 3NF: Eliminate delivery dependencies In the non-primary key field. Suppose a field can deduce that there is also a field, which is called transitive dependency. Iv. the relationship between standardization and performance 1, in order to meet a certain business objectives. Database p
, otherwise the machine memory is too small, causing frequent swap writes. To upgrade the memory or expand it at this time Locked% Locked time percentage, try to control it below 50% idx Miss% index Miss percentage. If it's too high, consider whether the index is less . Q t|r|w When MongoDB receives too many commands and the database is locked and cannot be completed, it joins the command to the queue. This column shows the length of the tota
Label:Environment: Server-side SDE 10.0 Oracle 11.2, client plsql 11,oracle 11.2 For debugging convenience, the following test is to extract SQL to do on the Plsql Demand is known as the point coordinate of a polygon, to be in a line layer, do relational intersect spatial query, the original
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
this point you will find a log file named after your native name in the Data folder in the MySQL installation directory The slow query operation is performed again at this time Open log file discovery occurrence record Later, you can only check the log file periodically to find the slow query statement. Note: aft
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 excha
to organize the report. Here I use python [The final result is as follows] [Technical Details] 1. modify my. cnf # The overall effect is that both the table and log file are enabled globally, but only the table is written for general_log, And the slow_query_log and log files are recorded.General_log = 1 # enable the log slow_query_log = 1 # enable the log of mysql slow SQL # Setting will affect gene
Tags: performance optimization slow query MySQL database tuning databasefirst, find slow query The last thing we do is to prepare for the occurrence of slow queries, which allows us to find s
MySQL slow query can help us optimize the efficiency of the MySQL database. The following describes how to enable MySQL slow query to find SQL statements that affect the efficiency. During website operation, the website may sudden
returned by the user or set rowcount to restrict the operation of the line 22, in the SQL2000 before, generally do not use the following words: "Is NULL", "23. Use Query Analyzer to view query plans for SQL statements and evaluate whether the analysis is optimized for SQL. The average 20% of the code occupies 80% of t
In the daily development, often encounter the page open very slow situation, by excluding, determined, is the impact of the database, in order to quickly find the specific SQL, can be logged through the MySQL method.--Open the SQL execution logging functionSet global log_output= ' TABLE '; --Output to tableSet global l
Tags: optimizing index database MySQL Preface Recently help the company to optimize the database, with the previous learning, step-by-step learning knowledge for practice, finally is the speed rub up, a query originally to execute more than 1 minutes now only need 3 seconds. Now the study of what they think and use to summarize, on the one hand to consolidate kn
optimization strategy based on rules and cost estimates. 4. Parallel query queries optimize parallel conditions: 1. The number of available resources in the System 2.CPU 3. The specific algebraic operators in the operation within the same SQL, the query is divided into intra-operation parallelism and inter-operation parallel 5. Distributed
, pay attention to setting the Sql_no_cache1.where condition sheet, and lock the minimum return record table. This sentence means to apply the where of the query to the table the smallest number of records returned from the table began to look up, a single table each field query, to see which field of the highest degree of sensitivity 2.explain View execution plan, is consistent with 1 expected (from a tabl
A business scenario that requires a union query:The query is very slow and takes about 37 seconds:Direct replication SQL in the database client execution, fast, it is known that the reason for MyBatis, on-line search, you can configure fetchsize= "500", but the test results are the same, re-view
Tags: write generated bsp MySQL col alt units should be two kinds ofInput command:show variables like ' slow% ' You can find that Slow_query_log is OFF (default), indicating that the slow query log is not turned on Slow_query_log_file for slow query log file There are two
Tags: store style col MySQL share picture lob Div using indexfirst, MySQL's slow query log opening and storage 1, check whether the SQL records that do not use the index to the slow query log, view the log_queries_not_using_indexes variable; like "Log_queries_%" Results:
MySQL Database optimizationI. SQL and index optimizationHow do I find the problematic SQL?Use the MySQL slow query log to monitor efficiency issues with SQLTo see if the slow query log
[mysqld] under the AddThe code is as followsLog-slow-queries=/data/mysqldata/slowquery. Loglong_query_time=2DescriptionLog-slow-queries = F:/mysql/log/mysqlslowquery.For the slow query log storage location, generally this directory to have MySQL running account of the writa
slow. The 2 Big idea is to ask yourself first: is the index built? is the index built to fit? When we analyze a SQL slow, we need to consider whether the content of this SQL query is indexed? If not, what kind of index should be built? For example, we want to check a user f
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