Add dollar prefix support for money constants in MSSQL (#2285)

Author: solontsev

src/dialect/mod.rs

@@ -1047,6 +1047,12 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns true if this dialect supports `$` as a prefix for money literals
+    /// e.g. `SELECT $123.45` (SQL Server)
+    fn supports_dollar_as_money_prefix(&self) -> bool {
+        false
+    }
+
     /// Does the dialect support with clause in create index statement?
     /// e.g. `CREATE INDEX idx ON t WITH (key = value, key2)`
     fn supports_create_index_with_clause(&self) -> bool {

src/dialect/mssql.rs

@@ -65,6 +65,12 @@ impl Dialect for MsSqlDialect {
         true
     }
 
+    /// SQL Server supports `$` as a prefix for money literals
+    /// <https://learn.microsoft.com/en-us/sql/t-sql/data-types/constants-transact-sql?view=sql-server-ver17#money-constants>
+    fn supports_dollar_as_money_prefix(&self) -> bool {
+        true
+    }
+
     fn supports_connect_by(&self) -> bool {
         true
     }

src/tokenizer.rs

@@ -1966,6 +1966,19 @@ impl<'a> Tokenizer<'a> {
                     || matches!(ch, '$' if self.dialect.supports_dollar_placeholder())
             }));
 
+            // If the dialect supports a dollar sign as a money prefix (e.g. SQL Server),
+            // and the value so far is all digits, check for a decimal part, e.g. `$123.45`
+            if matches!(chars.peek(), Some('.'))
+                && self.dialect.supports_dollar_as_money_prefix()
+                && !value.is_empty()
+                && value.chars().all(|c| c.is_ascii_digit())
+            {
+                value.push('.');
+                chars.next();
+                value.push_str(&peeking_take_while(chars, |ch| ch.is_ascii_digit()));
+                return Ok(Token::Placeholder(format!("${value}")));
+            }
+
             // If the dialect does not support dollar-quoted strings, don't look for the end delimiter.
             if matches!(chars.peek(), Some('$')) && !self.dialect.supports_dollar_placeholder() {
                 chars.next();

tests/sqlparser_mssql.rs

@@ -2860,3 +2860,38 @@ fn parse_mssql_update_with_output_into() {
         "UPDATE employees SET salary = salary * 1.1 OUTPUT INSERTED.id, DELETED.salary, INSERTED.salary INTO @changes WHERE department = 'Engineering'",
     );
 }
+
+#[test]
+fn parse_mssql_money_constants() {
+    ms().verified_only_select("SELECT CEILING($123.45)");
+
+    let select = ms().verified_only_select("SELECT $123.45");
+    assert_eq!(
+        &Expr::Value(Value::Placeholder("$123.45".to_string()).with_empty_span()),
+        expr_from_projection(only(&select.projection)),
+    );
+
+    let select = ms().verified_only_select("SELECT $0.99");
+    assert_eq!(
+        &Expr::Value(Value::Placeholder("$0.99".to_string()).with_empty_span()),
+        expr_from_projection(only(&select.projection)),
+    );
+
+    let select = ms().verified_only_select("SELECT $0.0");
+    assert_eq!(
+        &Expr::Value(Value::Placeholder("$0.0".to_string()).with_empty_span()),
+        expr_from_projection(only(&select.projection)),
+    );
+
+    let select = ms().verified_only_select("SELECT $123");
+    assert_eq!(
+        &Expr::Value(Value::Placeholder("$123".to_string()).with_empty_span()),
+        expr_from_projection(only(&select.projection)),
+    );
+
+    let select = ms().verified_only_select("SELECT $0");
+    assert_eq!(
+        &Expr::Value(Value::Placeholder("$0".to_string()).with_empty_span()),
+        expr_from_projection(only(&select.projection)),
+    );
+}