The things that SQL optimizes

Series Theme Bar, this essay, is mainly to record the LZ everyday feel favor SQL optimization of some small details

1. Like, you can use index query when you start not fuzzy query, that is, like the first keyword is specific, not "%"

1 # # Not available index, global, not recommended2EXPLAINSELECT  *  fromTable_aWHEREColumn_a like '% keyword%';3EXPLAINSELECT  *  fromTable_aWHEREColumn_a like '% Keyword';4 5 # # Available indexes, recommended6EXPLAINSELECT  *  fromTable_aWHEREColumn_a like 'off% key word%';7EXPLAINSELECT  *  fromTable_aWHEREColumn_a like 'off% key word';

As above, this field needs to be the criteria of the index query, if we are a large amount of data, insert the value of the field, it is recommended to add a common prefix, convenient like the use of indexes, improve query speed

#待续

As usual, the follow-up will slowly add

The things that SQL optimizes