是否会添加不必要的比较以获得结果但是减少选择是一个好主意？

For example:

例如：

Table(id/name/code)

1/blue/1
2/red/1
4/green/1
4/../1
../../1
2552/yellow/0

would be same query to:

将是相同的查询：

$select = "SELECT * FROM table WHERE name='yellow' AND code = '0'"

than to:?

而不是：？

 $select = "SELECT * FROM table WHERE name='yellow'"

I mean, i get same results, but is it same query? better? worse?

我的意思是，我得到相同的结果，但它是相同的查询？更好？更差？

1 个解决方案

#1

It will depend on the indexes that are associated with the table and the amount of data in the table.

它将取决于与表关联的索引以及表中的数据量。

If there's a large amount of data and you don't have an index on the name column, but an index on the code column, you would see a greater performance improvement with the code = '0'condition.

如果存在大量数据并且您没有名称列上的索引，而是代码列上的索引，那么使用code ='0'条件会有更大的性能提升。

If you have index on each column, the distribution of data in the table will determine which index is best. If you don't have the code = '0'condition, then that index will not be evaluated.

如果每列都有索引，则表中的数据分布将确定哪个索引最佳。如果您没有code ='0'条件，则不会评估该索引。

Table(id/name/code)

1 个解决方案

#1

更多相关文章

随机推荐