# DataFusion SQL Query Planner
This crate provides a general purpose SQL query planner that can parse SQL and translate queries into logical
plans. Although this crate is used by the [DataFusion](df) query engine, it was designed to be easily usable from any
project that requires a SQL query planner and does not make any assumptions about how the resulting logical plan
will be translated to a physical plan. For example, there is no concept of row-based versus columnar execution in the
logical plan.
## Example Usage
See the [examples](examples) directory for fully working examples.
Here is an example of producing a logical plan from a SQL string.
```rust,ignore
fn main() {
let sql = "SELECT \
c.id, c.first_name, c.last_name, \
COUNT(*) as num_orders, \
SUM(o.price) AS total_price, \
SUM(o.price * s.sales_tax) AS state_tax \
FROM customer c \
JOIN state s ON c.state = s.id \
JOIN orders o ON c.id = o.customer_id \
WHERE o.price > 0 \
AND c.last_name LIKE 'G%' \
GROUP BY 1, 2, 3 \
ORDER BY state_tax DESC";
// parse the SQL
let dialect = GenericDialect {}; // or AnsiDialect, or your own dialect ...
let ast = Parser::parse_sql(&dialect, sql).unwrap();
let statement = &ast[0];
// create a logical query plan
let schema_provider = MySchemaProvider::new();
let sql_to_rel = SqlToRel::new(&schema_provider);
let plan = sql_to_rel.sql_statement_to_plan(statement.clone()).unwrap();
// show the plan
println!("{:?}", plan);
}
```
This is the logical plan that is produced from this example. Note that this is an **unoptimized**
logical plan. The [datafusion-optimizer](https://crates.io/crates/datafusion-optimizer) crate provides a query
optimizer that can be applied to plans produced by this crate.
```
Sort: #state_tax DESC NULLS FIRST
Projection: #c.id, #c.first_name, #c.last_name, #COUNT(UInt8(1)) AS num_orders, #SUM(o.price) AS total_price, #SUM(o.price * s.sales_tax) AS state_tax
Aggregate: groupBy=[[#c.id, #c.first_name, #c.last_name]], aggr=[[COUNT(UInt8(1)), SUM(#o.price), SUM(#o.price * #s.sales_tax)]]
Filter: #o.price > Int64(0) AND #c.last_name LIKE Utf8("G%")
Inner Join: #c.id = #o.customer_id
Inner Join: #c.state = #s.id
SubqueryAlias: c
TableScan: customer
SubqueryAlias: s
TableScan: state
SubqueryAlias: o
TableScan: orders
```
[df]: https://crates.io/crates/datafusion