What are the classifications of mysql indexes?
MySQL indexes are divided into the following types: 1. Ordinary index: matching value, range or prefix; 2. Unique index: ensuring unique value; 3. Primary key index: unique index of the primary key column; 4. Foreign key index : Points to the primary key of another table; 5. Full-text index: full-text search; 6. Hash index: equal match search; 7. Spatial index: geospatial search; 8. Composite index: search based on multiple columns.
MySQL Index Classification
Index is a structure in MySQL used to quickly find and retrieve data. They help reduce the time required to scan a data table by creating pointers to data in the table. There are the following types of indexes in MySQL:
1. Ordinary index (BTREE index)
- The most common index type.
- Can be used to match column value, range or prefix search.
- Can have multiple columns.
2. Unique index
- Ensure that the column value is unique in the table.
- Can speed up finding records based on unique columns.
- Can have multiple columns.
3. Primary key index
- Special type of primary key, unique and non-empty.
- MySQL automatically adds the table's primary key to the primary key index.
4. Foreign key index
- An index pointing to the primary key of another table.
- Can establish relationships between tables and enforce integrity constraints.
5. Full-text index (FTS index)
- For full-text search on text and numeric fields.
- Allows searching based on keywords or phrases.
6. Hash index
- maps key values directly to data pages.
- Applies only to equal match searches.
- Faster than BTREE index, but takes up more storage.
7. Spatial index
- is used to index geospatial data.
- Supports search based on location, range and distance.
8. Composite index
- An index composed of multiple columns.
- Can speed up searches based on multiple columns.
- The order and order of each column is important.
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