Incorrect usage of indexes caused by SQL statements

Incorrect usage of indexes caused by SQL statements

When you create an index on the database, you find that the index is not used.

To a large extent, it is because you did not have the correct method when writing SQL statements.

In several cases, the index may not be used:

1. Use null, is null, and other judgment conditions in the index row.

2. Using the <> judgment Statement on the index row will result in a fast full-text index.

3. In the where query condition, index rows are compared using functions.

4. The data type of the index row does not match the determined data type.