MsSQL TRY_CONVERT (#1477)

Author: yoavcloud

src/ast/mod.rs

@@ -669,6 +669,9 @@ pub enum Expr {
     },
     /// CONVERT a value to a different data type or character encoding. e.g. `CONVERT(foo USING utf8mb4)`
     Convert {
+        /// CONVERT (false) or TRY_CONVERT (true)
+        /// <https://learn.microsoft.com/en-us/sql/t-sql/functions/try-convert-transact-sql?view=sql-server-ver16>
+        is_try: bool,
         /// The expression to convert
         expr: Box<Expr>,
         /// The target data type
@@ -1371,13 +1374,14 @@ impl fmt::Display for Expr {
                 }
             }
             Expr::Convert {
+                is_try,
                 expr,
                 target_before_value,
                 data_type,
                 charset,
                 styles,
             } => {
-                write!(f, "CONVERT(")?;
+                write!(f, "{}CONVERT(", if *is_try { "TRY_" } else { "" })?;
                 if let Some(data_type) = data_type {
                     if let Some(charset) = charset {
                         write!(f, "{expr}, {data_type} CHARACTER SET {charset}")

src/dialect/generic.rs

@@ -107,4 +107,8 @@ impl Dialect for GenericDialect {
     fn supports_asc_desc_in_column_definition(&self) -> bool {
         true
     }
+
+    fn supports_try_convert(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -585,6 +585,11 @@ pub trait Dialect: Debug + Any {
     fn supports_eq_alias_assigment(&self) -> bool {
         false
     }
+
+    /// Returns true if this dialect supports the `TRY_CONVERT` function
+    fn supports_try_convert(&self) -> bool {
+        false
+    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/mssql.rs

@@ -53,4 +53,8 @@ impl Dialect for MsSqlDialect {
     fn supports_eq_alias_assigment(&self) -> bool {
         true
     }
+
+    fn supports_try_convert(&self) -> bool {
+        true
+    }
 }

src/keywords.rs

@@ -771,6 +771,7 @@ define_keywords!(
     TRUE,
     TRUNCATE,
     TRY_CAST,
+    TRY_CONVERT,
     TUPLE,
     TYPE,
     UESCAPE,

src/parser/mod.rs

@@ -1023,7 +1023,8 @@ impl<'a> Parser<'a> {
                     self.parse_time_functions(ObjectName(vec![w.to_ident()]))
                 }
                 Keyword::CASE => self.parse_case_expr(),
-                Keyword::CONVERT => self.parse_convert_expr(),
+                Keyword::CONVERT => self.parse_convert_expr(false),
+                Keyword::TRY_CONVERT if self.dialect.supports_try_convert() => self.parse_convert_expr(true),
                 Keyword::CAST => self.parse_cast_expr(CastKind::Cast),
                 Keyword::TRY_CAST => self.parse_cast_expr(CastKind::TryCast),
                 Keyword::SAFE_CAST => self.parse_cast_expr(CastKind::SafeCast),
@@ -1614,7 +1615,7 @@ impl<'a> Parser<'a> {
     }
 
     /// mssql-like convert function
-    fn parse_mssql_convert(&mut self) -> Result<Expr, ParserError> {
+    fn parse_mssql_convert(&mut self, is_try: bool) -> Result<Expr, ParserError> {
         self.expect_token(&Token::LParen)?;
         let data_type = self.parse_data_type()?;
         self.expect_token(&Token::Comma)?;
@@ -1626,6 +1627,7 @@ impl<'a> Parser<'a> {
         };
         self.expect_token(&Token::RParen)?;
         Ok(Expr::Convert {
+            is_try,
             expr: Box::new(expr),
             data_type: Some(data_type),
             charset: None,
@@ -1638,16 +1640,17 @@ impl<'a> Parser<'a> {
     ///  - `CONVERT('héhé' USING utf8mb4)` (MySQL)
     ///  - `CONVERT('héhé', CHAR CHARACTER SET utf8mb4)` (MySQL)
     ///  - `CONVERT(DECIMAL(10, 5), 42)` (MSSQL) - the type comes first
-    pub fn parse_convert_expr(&mut self) -> Result<Expr, ParserError> {
+    pub fn parse_convert_expr(&mut self, is_try: bool) -> Result<Expr, ParserError> {
         if self.dialect.convert_type_before_value() {
-            return self.parse_mssql_convert();
+            return self.parse_mssql_convert(is_try);
         }
         self.expect_token(&Token::LParen)?;
         let expr = self.parse_expr()?;
         if self.parse_keyword(Keyword::USING) {
             let charset = self.parse_object_name(false)?;
             self.expect_token(&Token::RParen)?;
             return Ok(Expr::Convert {
+                is_try,
                 expr: Box::new(expr),
                 data_type: None,
                 charset: Some(charset),
@@ -1664,6 +1667,7 @@ impl<'a> Parser<'a> {
         };
         self.expect_token(&Token::RParen)?;
         Ok(Expr::Convert {
+            is_try,
             expr: Box::new(expr),
             data_type: Some(data_type),
             charset,

tests/sqlparser_common.rs

@@ -11449,3 +11449,14 @@ fn test_alias_equal_expr() {
     let expected = r#"SELECT x = (a * b) FROM some_table"#;
     let _ = dialects.one_statement_parses_to(sql, expected);
 }
+
+#[test]
+fn test_try_convert() {
+    let dialects =
+        all_dialects_where(|d| d.supports_try_convert() && d.convert_type_before_value());
+    dialects.verified_expr("TRY_CONVERT(VARCHAR(MAX), 'foo')");
+
+    let dialects =
+        all_dialects_where(|d| d.supports_try_convert() && !d.convert_type_before_value());
+    dialects.verified_expr("TRY_CONVERT('foo', VARCHAR(MAX))");
+}

tests/sqlparser_mssql.rs

@@ -464,6 +464,7 @@ fn parse_cast_varchar_max() {
 fn parse_convert() {
     let sql = "CONVERT(INT, 1, 2, 3, NULL)";
     let Expr::Convert {
+        is_try,
         expr,
         data_type,
         charset,
@@ -473,6 +474,7 @@ fn parse_convert() {
     else {
         unreachable!()
     };
+    assert!(!is_try);
     assert_eq!(Expr::Value(number("1")), *expr);
     assert_eq!(Some(DataType::Int(None)), data_type);
     assert!(charset.is_none());