add support for JSON_TABLE

see https://dev.mysql.com/doc/refman/8.0/en/json-table-functions.html
and
https://modern-sql.com/blog/2017-06/whats-new-in-sql-2016#json_table

Fixes sqlpage/SQLPage#146

src/ast/mod.rs

@@ -38,11 +38,12 @@ pub use self::ddl::{
 pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
     Cte, Distinct, ExceptSelectItem, ExcludeSelectItem, Fetch, ForClause, ForJson, ForXml,
-    GroupByExpr, IdentWithAlias, Join, JoinConstraint, JoinOperator, LateralView, LockClause,
-    LockType, NamedWindowDefinition, NonBlock, Offset, OffsetRows, OrderByExpr, Query,
-    RenameSelectItem, ReplaceSelectElement, ReplaceSelectItem, Select, SelectInto, SelectItem,
-    SetExpr, SetOperator, SetQuantifier, Table, TableAlias, TableFactor, TableVersion,
-    TableWithJoins, Top, Values, WildcardAdditionalOptions, With,
+    GroupByExpr, IdentWithAlias, Join, JoinConstraint, JoinOperator, JsonTableColumn,
+    JsonTableColumnErrorHandling, LateralView, LockClause, LockType, NamedWindowDefinition,
+    NonBlock, Offset, OffsetRows, OrderByExpr, Query, RenameSelectItem, ReplaceSelectElement,
+    ReplaceSelectItem, Select, SelectInto, SelectItem, SetExpr, SetOperator, SetQuantifier, Table,
+    TableAlias, TableFactor, TableVersion, TableWithJoins, Top, Values, WildcardAdditionalOptions,
+    With,
 };
 pub use self::value::{
     escape_quoted_string, DateTimeField, DollarQuotedString, TrimWhereField, Value,

src/ast/query.rs

@@ -726,6 +726,33 @@ pub enum TableFactor {
         with_offset: bool,
         with_offset_alias: Option<Ident>,
     },
+    /// The `JSON_TABLE` table-valued function.
+    /// Part of the SQL standard, but implemented only by MySQL, Oracle, and DB2.
+    ///
+    /// <https://modern-sql.com/blog/2017-06/whats-new-in-sql-2016#json_table>
+    /// <https://dev.mysql.com/doc/refman/8.0/en/json-table-functions.html#function_json-table>
+    ///
+    /// ```sql
+    /// SELECT * FROM JSON_TABLE(
+    ///    '[{"a": 1, "b": 2}, {"a": 3, "b": 4}]',
+    ///    '$[*]' COLUMNS(
+    ///        a INT PATH '$.a' DEFAULT '0' ON EMPTY,
+    ///        b INT PATH '$.b' NULL ON ERROR
+    ///     )
+    /// ) AS jt;
+    /// ````
+    JsonTable {
+        /// The JSON expression to be evaluated. It must evaluate to a json string
+        json_expr: Expr,
+        /// The path to the array or object to be iterated over.
+        /// It must evaluate to a json array or object.
+        json_path: Value,
+        /// The columns to be extracted from each element of the array or object.
+        /// Each column must have a name and a type.
+        columns: Vec<JsonTableColumn>,
+        /// The alias for the table.
+        alias: Option<TableAlias>,
+    },
     /// Represents a parenthesized table factor. The SQL spec only allows a
     /// join expression (`(foo <JOIN> bar [ <JOIN> baz ... ])`) to be nested,
     /// possibly several times.
@@ -848,6 +875,22 @@ impl fmt::Display for TableFactor {
                 }
                 Ok(())
             }
+            TableFactor::JsonTable {
+                json_expr,
+                json_path,
+                columns,
+                alias,
+            } => {
+                write!(
+                    f,
+                    "JSON_TABLE({json_expr}, {json_path} COLUMNS({columns}))",
+                    columns = display_comma_separated(columns)
+                )?;
+                if let Some(alias) = alias {
+                    write!(f, " AS {alias}")?;
+                }
+                Ok(())
+            }
             TableFactor::NestedJoin {
                 table_with_joins,
                 alias,
@@ -1443,3 +1486,74 @@ impl fmt::Display for ForJson {
         }
     }
 }
+
+/// A single column definition in MySQL's `JSON_TABLE` table valued function.
+/// ```sql
+/// SELECT *
+/// FROM JSON_TABLE(
+///     '["a", "b"]',
+///     '$[*]' COLUMNS (
+///         value VARCHAR(20) PATH '$'
+///     )
+/// ) AS jt;
+/// ```
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct JsonTableColumn {
+    /// The name of the column to be extracted.
+    pub name: Ident,
+    /// The type of the column to be extracted.
+    pub r#type: DataType,
+    /// The path to the column to be extracted. Must be a literal string.
+    pub path: Value,
+    /// true if the column is a boolean set to true if the given path exists
+    pub exists: bool,
+    /// The empty handling clause of the column
+    pub on_empty: Option<JsonTableColumnErrorHandling>,
+    /// The error handling clause of the column
+    pub on_error: Option<JsonTableColumnErrorHandling>,
+}
+
+impl fmt::Display for JsonTableColumn {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "{} {}{} PATH {}",
+            self.name,
+            self.r#type,
+            if self.exists { " EXISTS" } else { "" },
+            self.path
+        )?;
+        if let Some(on_empty) = &self.on_empty {
+            write!(f, " {} ON EMPTY", on_empty)?;
+        }
+        if let Some(on_error) = &self.on_error {
+            write!(f, " {} ON ERROR", on_error)?;
+        }
+        Ok(())
+    }
+}
+
+/// Stores the error handling clause of a `JSON_TABLE` table valued function:
+/// {NULL | DEFAULT json_string | ERROR} ON {ERROR | EMPTY }
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum JsonTableColumnErrorHandling {
+    Null,
+    Default(Value),
+    Error,
+}
+
+impl fmt::Display for JsonTableColumnErrorHandling {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            JsonTableColumnErrorHandling::Null => write!(f, "NULL"),
+            JsonTableColumnErrorHandling::Default(json_string) => {
+                write!(f, "DEFAULT {}", json_string)
+            }
+            JsonTableColumnErrorHandling::Error => write!(f, "ERROR"),
+        }
+    }
+}

src/keywords.rs

@@ -237,6 +237,7 @@ define_keywords!(
     ELEMENT,
     ELEMENTS,
     ELSE,
+    EMPTY,
     ENCODING,
     ENCRYPTION,
     END,
@@ -353,6 +354,7 @@ define_keywords!(
     JOIN,
     JSON,
     JSONFILE,
+    JSON_TABLE,
     JULIAN,
     KEY,
     KILL,

src/parser/mod.rs

@@ -6886,6 +6886,7 @@ impl<'a> Parser<'a> {
                         | TableFactor::Table { alias, .. }
                         | TableFactor::Function { alias, .. }
                         | TableFactor::UNNEST { alias, .. }
+                        | TableFactor::JsonTable { alias, .. }
                         | TableFactor::TableFunction { alias, .. }
                         | TableFactor::Pivot { alias, .. }
                         | TableFactor::Unpivot { alias, .. }
@@ -6944,6 +6945,23 @@ impl<'a> Parser<'a> {
                 with_offset,
                 with_offset_alias,
             })
+        } else if self.parse_keyword(Keyword::JSON_TABLE) {
+            self.expect_token(&Token::LParen)?;
+            let json_expr = self.parse_expr()?;
+            self.expect_token(&Token::Comma)?;
+            let json_path = self.parse_value()?;
+            self.expect_keyword(Keyword::COLUMNS)?;
+            self.expect_token(&Token::LParen)?;
+            let columns = self.parse_comma_separated(Parser::parse_json_table_column_def)?;
+            self.expect_token(&Token::RParen)?;
+            self.expect_token(&Token::RParen)?;
+            let alias = self.parse_optional_table_alias(keywords::RESERVED_FOR_TABLE_ALIAS)?;
+            Ok(TableFactor::JsonTable {
+                json_expr,
+                json_path,
+                columns,
+                alias,
+            })
         } else {
             let name = self.parse_object_name()?;
 
@@ -7014,6 +7032,50 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Parses MySQL's JSON_TABLE column definition.
+    /// For example: `id INT EXISTS PATH '$' DEFAULT '0' ON EMPTY ERROR ON ERROR`
+    pub fn parse_json_table_column_def(&mut self) -> Result<JsonTableColumn, ParserError> {
+        let name = self.parse_identifier()?;
+        let r#type = self.parse_data_type()?;
+        let exists = self.parse_keyword(Keyword::EXISTS);
+        self.expect_keyword(Keyword::PATH)?;
+        let path = self.parse_value()?;
+        let mut on_empty = None;
+        let mut on_error = None;
+        while let Some(error_handling) = self.parse_json_table_column_error_handling()? {
+            if self.parse_keyword(Keyword::EMPTY) {
+                on_empty = Some(error_handling);
+            } else {
+                self.expect_keyword(Keyword::ERROR)?;
+                on_error = Some(error_handling);
+            }
+        }
+        Ok(JsonTableColumn {
+            name,
+            r#type,
+            path,
+            exists,
+            on_empty,
+            on_error,
+        })
+    }
+
+    fn parse_json_table_column_error_handling(
+        &mut self,
+    ) -> Result<Option<JsonTableColumnErrorHandling>, ParserError> {
+        let res = if self.parse_keyword(Keyword::NULL) {
+            JsonTableColumnErrorHandling::Null
+        } else if self.parse_keyword(Keyword::ERROR) {
+            JsonTableColumnErrorHandling::Error
+        } else if self.parse_keyword(Keyword::DEFAULT) {
+            JsonTableColumnErrorHandling::Default(self.parse_value()?)
+        } else {
+            return Ok(None);
+        };
+        self.expect_keyword(Keyword::ON)?;
+        Ok(Some(res))
+    }
+
     pub fn parse_derived_table_factor(
         &mut self,
         lateral: IsLateral,

tests/sqlparser_mysql.rs

@@ -1870,3 +1870,57 @@ fn parse_convert_using() {
     // with a type + a charset
     mysql().verified_only_select("SELECT CONVERT('test', CHAR CHARACTER SET utf8mb4)");
 }
+
+#[test]
+fn parse_json_table() {
+    mysql().verified_only_select("SELECT * FROM JSON_TABLE('[[1, 2], [3, 4]]', '$[*]' COLUMNS(a INT PATH '$[0]', b INT PATH '$[1]')) AS t");
+    mysql().verified_only_select(
+        r#"SELECT * FROM JSON_TABLE('["x", "y"]', '$[*]' COLUMNS(a VARCHAR(20) PATH '$')) AS t"#,
+    );
+    // with a bound parameter
+    mysql().verified_only_select(
+        r#"SELECT * FROM JSON_TABLE(?, '$[*]' COLUMNS(a VARCHAR(20) PATH '$')) AS t"#,
+    );
+    // quote escaping
+    mysql().verified_only_select(r#"SELECT * FROM JSON_TABLE('{"''": [1,2,3]}', '$."''"[*]' COLUMNS(a VARCHAR(20) PATH '$')) AS t"#);
+    // double quotes
+    mysql().verified_only_select(
+        r#"SELECT * FROM JSON_TABLE("[]", "$[*]" COLUMNS(a VARCHAR(20) PATH "$")) AS t"#,
+    );
+    // exists
+    mysql().verified_only_select(r#"SELECT * FROM JSON_TABLE('[{}, {"x":1}]', '$[*]' COLUMNS(x INT EXISTS PATH '$.x')) AS t"#);
+    // error handling
+    mysql().verified_only_select(
+        r#"SELECT * FROM JSON_TABLE('[1,2]', '$[*]' COLUMNS(x INT PATH '$' ERROR ON ERROR)) AS t"#,
+    );
+    mysql().verified_only_select(
+        r#"SELECT * FROM JSON_TABLE('[1,2]', '$[*]' COLUMNS(x INT PATH '$' ERROR ON EMPTY)) AS t"#,
+    );
+    mysql().verified_only_select(r#"SELECT * FROM JSON_TABLE('[1,2]', '$[*]' COLUMNS(x INT PATH '$' ERROR ON EMPTY DEFAULT '0' ON ERROR)) AS t"#);
+    assert_eq!(
+        mysql()
+            .verified_only_select(
+                r#"SELECT * FROM JSON_TABLE('[1,2]', '$[*]' COLUMNS(x INT PATH '$' DEFAULT '0' ON EMPTY NULL ON ERROR)) AS t"#
+            )
+            .from[0]
+            .relation,
+        TableFactor::JsonTable {
+            json_expr: Expr::Value(Value::SingleQuotedString("[1,2]".to_string())),
+            json_path: Value::SingleQuotedString("$[*]".to_string()),
+            columns: vec![
+                JsonTableColumn {
+                    name: Ident::new("x"),
+                    r#type: DataType::Int(None),
+                    path: Value::SingleQuotedString("$".to_string()),
+                    exists: false,
+                    on_empty: Some(JsonTableColumnErrorHandling::Default(Value::SingleQuotedString("0".to_string()))),
+                    on_error: Some(JsonTableColumnErrorHandling::Null),
+                },
+            ],
+            alias: Some(TableAlias {
+                name: Ident::new("t"),
+                columns: vec![],
+            }),
+        }
+    );
+}