Add support for == operator for Sqlite (#970)

Author: marhoily

src/tokenizer.rs

@@ -885,6 +885,7 @@ impl<'a> Tokenizer<'a> {
                     chars.next(); // consume
                     match chars.peek() {
                         Some('>') => self.consume_and_return(chars, Token::RArrow),
+                        Some('=') => self.consume_and_return(chars, Token::DoubleEq),
                         _ => Ok(Some(Token::Eq)),
                     }
                 }

tests/sqlparser_sqlite.rs

@@ -61,6 +61,14 @@ fn parse_create_virtual_table() {
     sqlite_and_generic().verified_stmt(sql);
 }
 
+#[test]
+fn double_equality_operator() {
+    // Sqlite supports this operator: https://www.sqlite.org/lang_expr.html#binaryops
+    let input = "SELECT a==b FROM t";
+    let expected = "SELECT a = b FROM t";
+    let _ = sqlite_and_generic().one_statement_parses_to(input, expected);
+}
+
 #[test]
 fn parse_create_table_auto_increment() {
     let sql = "CREATE TABLE foo (bar INT PRIMARY KEY AUTOINCREMENT)";