The technique of data normalization is about correct ways of partitioning the data among tables to minimize data redundancy and maximize the speed of retrieval.
数据正规化技术是为将数据正确地保存再各个标准，从而使数据冗余达到最小，存取速度达到最高。
2
To speed searches, you may be able to rearrange your tables and, thus, simplify the underlying queries. table and SQL query optimization are highly dependent on your schema and engine.
要加速搜索，您可以重新安排表，并由此简化底层查询表和SQL查询优化高度依赖于模式和引擎。
3
Correlated subqueries will greatly degrade the speed of data retrieval, especially for non-selective queries on huge tables with millions of rows and with no index.