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4 wrz 2018 · A composite index is only useful when you're combining the tests with AND, not OR. When you have an OR condition, it has to test each column independently, but a composite index is a tree that has all the values of DNIS within their related ANI. So you should create separate indexes for each column.
MySQL can create composite indexes (that is, indexes on multiple columns). An index may consist of up to 16 columns. For certain data types, you can index a prefix of the column (see Section 10.3.5, “Column Indexes”).
If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas: CREATE INDEX idx_pname ON Persons (LastName, FirstName);
You can use this syntax to add an index and control the kind of index (HASH or BTREE). create index your_index_name on your_table_name(your_column_name) using HASH; or. create index your_index_name on your_table_name(your_column_name) using BTREE;
Creating multi-valued Indexes. You can create a multi-valued index in a CREATE TABLE, ALTER TABLE, or CREATE INDEX statement. This requires using CAST(... AS ... ARRAY) in the index definition, which casts same-typed scalar values in a JSON array to an SQL data type array. A virtual column is then generated transparently with the values in the ...
MySQL allows you to create a composite index that consists of up to 16 columns. A composite index is also known as a multiple-column index. The query optimizer uses the composite indexes for queries that test all columns in the index, or queries that test the first columns, the first two columns, and so on.
To create an index for a column or a list of columns, you specify the index name, the table to which the index belongs, and the column list. For example, to add a new index for the column c4, you use the following statement:
