# Expression Index (Continue...)
+ The optimizer can choose to use an expression index for a query when the expression in the query statement matches the expression in the expression index
```
SELECT lower(col1) FROM t;
SELECT * FROM t WHERE lower(col1) = "a";
SELECT * FROM t WHERE lower(col1) BETWEEN "a" AND "b";
SELECT * FROM t ORDER BY lower(col1);
SELECT min(col1) FROM t GROUP BY lower(col1);
```
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Expression index
- When the expression in the query statement matches the expression in the expression index, the optimizer can choose to use the expression index for the query
```
SELECT lower(col1) FROM t;
SELECT * FROM t WHERE lower(col1) = "a";
SELECT * FROM t WHERE lower(col1) BETWEEN "a" AND "b";
SELECT * FROM t ORDER BY lower(col1);
SELECT min(col1) FROM t GROUP BY lower(col1);
```