建立如此结构的数据表,并插入110万条随机记录,进行查询性能测试。 插入110万条随机记录后,数据表的大小为102MB。 现在使用phpMyAdmin自带的SQL查询器进行性能分析。 下面进行带索引的模式下查询测试: A. 随机的字符型字段全匹配查询,用时 0.0005(S) B
建立如此结构的数据表,并插入110万条随机记录,进行查询性能测试。
插入110万条随机记录后,数据表的大小为102MB。
现在使用phpMyAdmin自带的SQL查询器进行性能分析。
下面进行带索引的模式下查询测试:
A. 随机的字符型字段全匹配查询,用时 0.0005(S)
B.随机的主键查询,用时 0.0005(S)
C.随机的使用字符函数查询,用时 0.4482(S)
D.使用LIKE模式一查询,用时 0.0007(S)
E.使用LIKE模式二查询,用时 0.7361(S)
下面是删除了索引的情况下进行测试:
A. 随机的字符型字段全匹配查询,用时 0.3439(S)
B.随机的主键查询,用时 0.0004(S)
C.随机的使用字符函数查询,用时 0.4882(S)
D.使用LIKE模式一查询,用时 0.3487(S)
E.使用LIKE模式二查询,用时 0.7339(S)
结论:
对字段进行简单查询的情况下,如果字段建立了索引,查询速度远快于没有建索引的情况。使用MySQL函数的查询即使在建立了索引的情况下,速度依然跟没建索引的情况差不多。在使用 LIKE的 xxx%模式时候,有索引的情况远比没索引的要快,但 %xxx%模式在有索引和没索引的情况一样。

MySQL functions can be used for data processing and calculation. 1. Basic usage includes string processing, date calculation and mathematical operations. 2. Advanced usage involves combining multiple functions to implement complex operations. 3. Performance optimization requires avoiding the use of functions in the WHERE clause and using GROUPBY and temporary tables.

Efficient methods for batch inserting data in MySQL include: 1. Using INSERTINTO...VALUES syntax, 2. Using LOADDATAINFILE command, 3. Using transaction processing, 4. Adjust batch size, 5. Disable indexing, 6. Using INSERTIGNORE or INSERT...ONDUPLICATEKEYUPDATE, these methods can significantly improve database operation efficiency.

In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

Use the EXPLAIN command to analyze the execution plan of MySQL queries. 1. The EXPLAIN command displays the execution plan of the query to help find performance bottlenecks. 2. The execution plan includes fields such as id, select_type, table, type, possible_keys, key, key_len, ref, rows and Extra. 3. According to the execution plan, you can optimize queries by adding indexes, avoiding full table scans, optimizing JOIN operations, and using overlay indexes.

Subqueries can improve the efficiency of MySQL query. 1) Subquery simplifies complex query logic, such as filtering data and calculating aggregated values. 2) MySQL optimizer may convert subqueries to JOIN operations to improve performance. 3) Using EXISTS instead of IN can avoid multiple rows returning errors. 4) Optimization strategies include avoiding related subqueries, using EXISTS, index optimization, and avoiding subquery nesting.

Methods for configuring character sets and collations in MySQL include: 1. Setting the character sets and collations at the server level: SETNAMES'utf8'; SETCHARACTERSETutf8; SETCOLLATION_CONNECTION='utf8_general_ci'; 2. Create a database that uses specific character sets and collations: CREATEDATABASEexample_dbCHARACTERSETutf8COLLATEutf8_general_ci; 3. Specify character sets and collations when creating a table: CREATETABLEexample_table(idINT

To safely and thoroughly uninstall MySQL and clean all residual files, follow the following steps: 1. Stop MySQL service; 2. Uninstall MySQL packages; 3. Clean configuration files and data directories; 4. Verify that the uninstallation is thorough.

Renaming a database in MySQL requires indirect methods. The steps are as follows: 1. Create a new database; 2. Use mysqldump to export the old database; 3. Import the data into the new database; 4. Delete the old database.


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