Add support for MSSQL's SELECT TOP N syntax (#150)

Add support for MSSQL SELECT TOP (N) [PERCENT] [WITH TIES] syntax.

Author: alexkyllo

src/ast/mod.rs

@@ -27,7 +27,7 @@ pub use self::ddl::{
 pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
     Cte, Fetch, Join, JoinConstraint, JoinOperator, OrderByExpr, Query, Select, SelectItem,
-    SetExpr, SetOperator, TableAlias, TableFactor, TableWithJoins, Values,
+    SetExpr, SetOperator, TableAlias, TableFactor, TableWithJoins, Top, Values,
 };
 pub use self::value::{DateTimeField, Value};
 

src/ast/query.rs

@@ -114,6 +114,8 @@ impl fmt::Display for SetOperator {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Select {
     pub distinct: bool,
+    /// MSSQL syntax: `TOP (<N>) [ PERCENT ] [ WITH TIES ]`
+    pub top: Option<Top>,
     /// projection expressions
     pub projection: Vec<SelectItem>,
     /// FROM
@@ -128,12 +130,11 @@ pub struct Select {
 
 impl fmt::Display for Select {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "SELECT{} {}",
-            if self.distinct { " DISTINCT" } else { "" },
-            display_comma_separated(&self.projection)
-        )?;
+        write!(f, "SELECT{}", if self.distinct { " DISTINCT" } else { "" })?;
+        if let Some(ref top) = self.top {
+            write!(f, " {}", top)?;
+        }
+        write!(f, " {}", display_comma_separated(&self.projection))?;
         if !self.from.is_empty() {
             write!(f, " FROM {}", display_comma_separated(&self.from))?;
         }
@@ -408,6 +409,26 @@ impl fmt::Display for Fetch {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Top {
+    /// SQL semantic equivalent of LIMIT but with same structure as FETCH.
+    pub with_ties: bool,
+    pub percent: bool,
+    pub quantity: Option<Expr>,
+}
+
+impl fmt::Display for Top {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let extension = if self.with_ties { " WITH TIES" } else { "" };
+        if let Some(ref quantity) = self.quantity {
+            let percent = if self.percent { " PERCENT" } else { "" };
+            write!(f, "TOP ({}){}{}", quantity, percent, extension)
+        } else {
+            write!(f, "TOP{}", extension)
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Values(pub Vec<Vec<Expr>>);
 

src/dialect/keywords.rs

@@ -374,6 +374,7 @@ define_keywords!(
     TIMEZONE_HOUR,
     TIMEZONE_MINUTE,
     TO,
+    TOP,
     TRAILING,
     TRANSACTION,
     TRANSLATE,
@@ -426,7 +427,7 @@ define_keywords!(
 /// can be parsed unambiguously without looking ahead.
 pub const RESERVED_FOR_TABLE_ALIAS: &[&str] = &[
     // Reserved as both a table and a column alias:
-    WITH, SELECT, WHERE, GROUP, HAVING, ORDER, LIMIT, OFFSET, FETCH, UNION, EXCEPT, INTERSECT,
+    WITH, SELECT, WHERE, GROUP, HAVING, ORDER, TOP, LIMIT, OFFSET, FETCH, UNION, EXCEPT, INTERSECT,
     // Reserved only as a table alias in the `FROM`/`JOIN` clauses:
     ON, JOIN, INNER, CROSS, FULL, LEFT, RIGHT, NATURAL, USING,
     // for MSSQL-specific OUTER APPLY (seems reserved in most dialects)

src/parser.rs

@@ -783,7 +783,6 @@ impl Parser {
     }
 
     /// Bail out if the current token is not one of the expected keywords, or consume it if it is
-    #[must_use]
     pub fn expect_one_of_keywords(
         &mut self,
         keywords: &[&'static str],
@@ -1561,6 +1560,13 @@ impl Parser {
         if all && distinct {
             return parser_err!("Cannot specify both ALL and DISTINCT in SELECT");
         }
+
+        let top = if self.parse_keyword("TOP") {
+            Some(self.parse_top()?)
+        } else {
+            None
+        };
+
         let projection = self.parse_comma_separated(Parser::parse_select_item)?;
 
         // Note that for keywords to be properly handled here, they need to be
@@ -1594,6 +1600,7 @@ impl Parser {
 
         Ok(Select {
             distinct,
+            top,
             projection,
             from,
             selection,
@@ -1940,6 +1947,28 @@ impl Parser {
         Ok(OrderByExpr { expr, asc })
     }
 
+    /// Parse a TOP clause, MSSQL equivalent of LIMIT,
+    /// that follows after SELECT [DISTINCT].
+    pub fn parse_top(&mut self) -> Result<Top, ParserError> {
+        let quantity = if self.consume_token(&Token::LParen) {
+            let quantity = self.parse_expr()?;
+            self.expect_token(&Token::RParen)?;
+            Some(quantity)
+        } else {
+            Some(Expr::Value(self.parse_number_value()?))
+        };
+
+        let percent = self.parse_keyword("PERCENT");
+
+        let with_ties = self.parse_keywords(vec!["WITH", "TIES"]);
+
+        Ok(Top {
+            with_ties,
+            percent,
+            quantity,
+        })
+    }
+
     /// Parse a LIMIT clause
     pub fn parse_limit(&mut self) -> Result<Option<Expr>, ParserError> {
         if self.parse_keyword("ALL") {

src/tokenizer.rs

@@ -522,6 +522,7 @@ fn peeking_take_while(
 #[cfg(test)]
 mod tests {
     use super::super::dialect::GenericDialect;
+    use super::super::dialect::MsSqlDialect;
     use super::*;
 
     #[test]
@@ -782,6 +783,28 @@ mod tests {
         compare(expected, tokens);
     }
 
+    #[test]
+    fn tokenize_mssql_top() {
+        let sql = "SELECT TOP 5 [bar] FROM foo";
+        let dialect = MsSqlDialect {};
+        let mut tokenizer = Tokenizer::new(&dialect, sql);
+        let tokens = tokenizer.tokenize().unwrap();
+        let expected = vec![
+            Token::make_keyword("SELECT"),
+            Token::Whitespace(Whitespace::Space),
+            Token::make_keyword("TOP"),
+            Token::Whitespace(Whitespace::Space),
+            Token::Number(String::from("5")),
+            Token::Whitespace(Whitespace::Space),
+            Token::make_word("bar", Some('[')),
+            Token::Whitespace(Whitespace::Space),
+            Token::make_keyword("FROM"),
+            Token::Whitespace(Whitespace::Space),
+            Token::make_word("foo", None),
+        ];
+        compare(expected, tokens);
+    }
+
     fn compare(expected: Vec<Token>, actual: Vec<Token>) {
         //println!("------------------------------");
         //println!("tokens   = {:?}", actual);

tests/sqlparser_mssql.rs

@@ -68,6 +68,48 @@ fn parse_mssql_apply_join() {
     );
 }
 
+#[test]
+fn parse_mssql_top_paren() {
+    let sql = "SELECT TOP (5) * FROM foo";
+    let select = ms_and_generic().verified_only_select(sql);
+    let top = select.top.unwrap();
+    assert_eq!(Some(Expr::Value(number("5"))), top.quantity);
+    assert!(!top.percent);
+}
+
+#[test]
+fn parse_mssql_top_percent() {
+    let sql = "SELECT TOP (5) PERCENT * FROM foo";
+    let select = ms_and_generic().verified_only_select(sql);
+    let top = select.top.unwrap();
+    assert_eq!(Some(Expr::Value(number("5"))), top.quantity);
+    assert!(top.percent);
+}
+
+#[test]
+fn parse_mssql_top_with_ties() {
+    let sql = "SELECT TOP (5) WITH TIES * FROM foo";
+    let select = ms_and_generic().verified_only_select(sql);
+    let top = select.top.unwrap();
+    assert_eq!(Some(Expr::Value(number("5"))), top.quantity);
+    assert!(top.with_ties);
+}
+
+#[test]
+fn parse_mssql_top_percent_with_ties() {
+    let sql = "SELECT TOP (10) PERCENT WITH TIES * FROM foo";
+    let select = ms_and_generic().verified_only_select(sql);
+    let top = select.top.unwrap();
+    assert_eq!(Some(Expr::Value(number("10"))), top.quantity);
+    assert!(top.percent);
+}
+
+#[test]
+fn parse_mssql_top() {
+    let sql = "SELECT TOP 5 bar, baz FROM foo";
+    let _ = ms_and_generic().one_statement_parses_to(sql, "SELECT TOP (5) bar, baz FROM foo");
+}
+
 fn ms() -> TestedDialects {
     TestedDialects {
         dialects: vec![Box::new(MsSqlDialect {})],

tests/sqlparser_mysql.rs

@@ -77,7 +77,7 @@ fn parse_show_columns() {
         Statement::ShowColumns {
             extended: false,
             full: false,
-            table_name: table_name.clone(),
+            table_name: table_name,
             filter: Some(ShowStatementFilter::Where(
                 mysql_and_generic().verified_expr("1 = 2")
             )),