MySQL Index related

In 1.mysql, the inner join and the left join need to optimize the right table, while the starboard join needs to optimize the table.

2. Common indexes: Primary key, sort, range, where clause

No indexes: Big data types, such as text, image, bit

Behind like fields

3. Create an index: ALTER TABLE name add index index name (column 1, column 2, column 3 ....) ）;

Delete index: Drop the name of index x on table;

View index: Show index from table name \g

4. Index invalidation

Implicit conversions (must be double-quoted if the column type is a string), causing the index to fail

Index columns use functions, resulting in index invalidation

field after like,% plus in front and% plus on both sides cause index to fail

indexes are evaluated, resulting in index invalidation

! = does not exist cause index invalidation

MySQL Index related