Oracle中容易被忽略的地方-Mysql Tutorial-php.cn

Home

Database

Mysql Tutorial

Oracle中容易被忽略的地方

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 07, 2016 pm 05:13 PM

在我们写SQL语句时，我们有时候往往会忽略一些细节，下面是我通过自己动手操作和查阅资料总结出来的，如果有不对的地方，或者有补

在我们写SQL语句时，我们有时候往往会忽略一些细节，下面是我通过自己动手操作和查阅资料总结出来的，如果有不对的地方，或者有补充的，希望给我回复，大家互相学习。谢谢！

1、在进行全表扫描，而全表扫描的表的记录数超过100条，需要建立相应的索引或者更改查询条件，，使用索引查询，避免全表扫描。

2、在查询中，使用到like语句，尽量使用后模糊查询。例如：
select * from tablename where column_name like '%name%' --不会使用column_name上的索引

Oracle中容易被忽略的地方

select * from tablename where column_name like 'name%' --使用column_name上的索引

Oracle中容易被忽略的地方

3、如果in后面的子查询或者列表超过5个值，尽量不要使用in，而使用exists；使用not exists，而不使用not in.

4、无用的字段不要select出来。

更多Oracle相关信息见Oracle 专题页面 ?tid=12

linux

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

How do you handle database upgrades in MySQL?Apr 30, 2025 am 12:28 AM

The steps for upgrading MySQL database include: 1. Backup the database, 2. Stop the current MySQL service, 3. Install the new version of MySQL, 4. Start the new version of MySQL service, 5. Recover the database. Compatibility issues are required during the upgrade process, and advanced tools such as PerconaToolkit can be used for testing and optimization.

What are the different backup strategies you can use for MySQL?Apr 30, 2025 am 12:28 AM

MySQL backup policies include logical backup, physical backup, incremental backup, replication-based backup, and cloud backup. 1. Logical backup uses mysqldump to export database structure and data, which is suitable for small databases and version migrations. 2. Physical backups are fast and comprehensive by copying data files, but require database consistency. 3. Incremental backup uses binary logging to record changes, which is suitable for large databases. 4. Replication-based backup reduces the impact on the production system by backing up from the server. 5. Cloud backups such as AmazonRDS provide automation solutions, but costs and control need to be considered. When selecting a policy, database size, downtime tolerance, recovery time, and recovery point goals should be considered.

What is MySQL clustering?Apr 30, 2025 am 12:28 AM

MySQLclusteringenhancesdatabaserobustnessandscalabilitybydistributingdataacrossmultiplenodes.ItusestheNDBenginefordatareplicationandfaulttolerance,ensuringhighavailability.Setupinvolvesconfiguringmanagement,data,andSQLnodes,withcarefulmonitoringandpe

How do you optimize database schema design for performance in MySQL?Apr 30, 2025 am 12:27 AM

Optimizing database schema design in MySQL can improve performance through the following steps: 1. Index optimization: Create indexes on common query columns, balancing the overhead of query and inserting updates. 2. Table structure optimization: Reduce data redundancy through normalization or anti-normalization and improve access efficiency. 3. Data type selection: Use appropriate data types, such as INT instead of VARCHAR, to reduce storage space. 4. Partitioning and sub-table: For large data volumes, use partitioning and sub-table to disperse data to improve query and maintenance efficiency.

How can you optimize MySQL performance?Apr 30, 2025 am 12:26 AM

TooptimizeMySQLperformance,followthesesteps:1)Implementproperindexingtospeedupqueries,2)UseEXPLAINtoanalyzeandoptimizequeryperformance,3)Adjustserverconfigurationsettingslikeinnodb_buffer_pool_sizeandmax_connections,4)Usepartitioningforlargetablestoi

How to use MySQL functions for data processing and calculationApr 29, 2025 pm 04:21 PM

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.

An efficient way to batch insert data in MySQLApr 29, 2025 pm 04:18 PM

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.

Steps to add and delete fields to MySQL tablesApr 29, 2025 pm 04:15 PM

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.

See all articles