improved sql parser.

src/main/java/com/alibaba/druid/sql/ast/expr/SQLDateExpr.java

@@ -16,6 +16,7 @@
 package com.alibaba.druid.sql.ast.expr;
 
 import com.alibaba.druid.sql.ast.SQLDataType;
+import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.ast.SQLObject;
 import com.alibaba.druid.sql.ast.statement.SQLCharacterDataType;
@@ -29,26 +30,36 @@ import java.util.List;
 public class SQLDateExpr extends SQLExprImpl implements SQLLiteralExpr, SQLValuableExpr {
     public static final SQLDataType DEFAULT_DATA_TYPE = new SQLCharacterDataType("date");
 
-    private String literal;
+    private SQLExpr literal;
 
     public SQLDateExpr(){
 
     }
 
     public SQLDateExpr(String literal) {
-        this.literal = literal;
+        this.setLiteral(literal);
     }
 
-    public String getLiteral() {
+    public SQLExpr getLiteral() {
         return literal;
     }
 
     public void setLiteral(String literal) {
-        this.literal = literal;
+        setLiteral(new SQLCharExpr(literal));
+    }
+
+    public void setLiteral(SQLExpr x) {
+        if (x != null) {
+            x.setParent(this);
+        }
+        this.literal = x;
     }
 
     public String getValue() {
-        return literal;
+        if (literal instanceof SQLCharExpr) {
+            return ((SQLCharExpr) literal).getText();
+        }
+        return null;
     }
 
     @Override
@@ -88,7 +99,13 @@ public class SQLDateExpr extends SQLExprImpl implements SQLLiteralExpr, SQLValua
     }
 
     public SQLDateExpr clone() {
-        return new SQLDateExpr(literal);
+        SQLDateExpr x = new SQLDateExpr();
+
+        if (this.literal != null) {
+            x.setLiteral(literal.clone());
+        }
+
+        return x;
     }
 
     @Override

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -314,13 +314,11 @@ public class SQLExprParser extends SQLParser {
                 lexer.nextToken();
 
                 if (hash_lower == FnvHash.Constants.DATE
-                        && lexer.token == Token.LITERAL_CHARS
+                        && (lexer.token == Token.LITERAL_CHARS || lexer.token == Token.VARIANT)
                         && (JdbcConstants.ORACLE.equals(dbType)
                             || JdbcConstants.POSTGRESQL.equals(dbType)
                             || JdbcConstants.MYSQL.equals(dbType))) {
-                    String literal = lexer.stringVal();
-                    lexer.nextToken();
-
+                    SQLExpr literal = this.primary();
                     SQLDateExpr dateExpr = new SQLDateExpr();
                     dateExpr.setLiteral(literal);
                     sqlExpr = dateExpr;

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -5329,9 +5329,10 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
     }
 
     public boolean visit(SQLDateExpr x) {
-        print0(ucase ? "DATE '" : "date '");
-        print0(x.getLiteral());
-        print('\'');
+        SQLExpr literal = x.getLiteral();
+        print0(ucase ? "DATE " : "date ");
+        printExpr(literal);
+
         return false;
     }