# Lightweight transaction (LWT) statement

A lightweight transaction statement can be expressed just like any other statement, via `Session`, with the notable difference of having an additional consistency level parameter - the `serial_consistency_level`.

## Format of the statement

A lightweight transaction statement is not a separate type - it can be expressed just like any other statements: via `Statement`, `PreparedStatement`, batches, and so on. The difference lays in the statement string itself - when it contains a condition (e.g. `IF NOT EXISTS`), it becomes a lightweight transaction. It’s important to remember that CQL specification requires a separate, additional consistency level to be defined for LWT statements - `serial_consistency_level`. The serial consistency level can only be set to two values: `SerialConsistency::Serial` or `SerialConsistency::LocalSerial`. The “local” variant makes the transaction consistent only within the same datacenter. For convenience, ScyllaDB Rust Driver sets the default consistency level to `LocalSerial`, as it’s more commonly used. For cross-datacenter consistency, please remember to always override the default with `SerialConsistency::Serial`.

```rust
use scylla::statement::unprepared::Statement;
use scylla::statement::{Consistency, SerialConsistency};

// Create a Statement manually to change the Consistency to ONE
let mut my_statement: Statement = Statement::new("INSERT INTO ks.tab (a) VALUES(?) IF NOT EXISTS".to_string());
my_statement.set_consistency(Consistency::One);
// Use cross-datacenter serial consistency
my_statement.set_serial_consistency(Some(SerialConsistency::Serial));

// Insert a value into the table
let to_insert: i32 = 12345;
session.query_unpaged(my_statement, (to_insert,)).await?;
```

The rest of the API remains identical for LWT and non-LWT statements.

See [Statement API documentation](https://docs.rs/scylla/latest/scylla/statement/struct.Statement.html) for more options