improved oracle sql parser.

src/main/java/com/alibaba/druid/sql/dialect/oracle/parser/OracleLexer.java

@@ -51,6 +51,7 @@ public class OracleLexer extends Lexer {
         map.put("EXTRACT", Token.EXTRACT);
         map.put("GOTO", Token.GOTO);
         map.put("IF", Token.IF);
+        map.put("ELSIF", Token.ELSIF);
 
         map.put("LIMIT", Token.LIMIT);
         map.put("LOOP", Token.LOOP);

src/main/java/com/alibaba/druid/sql/dialect/oracle/parser/OracleSelectParser.java

@@ -148,7 +148,7 @@ public class OracleSelectParser extends SQLSelectParser {
 
                 select.setRestriction(checkOption);
             } else {
-                throw new ParserException("syntax error");
+                throw new ParserException("syntax error. " + lexer.info());
             }
         }
 

src/main/java/com/alibaba/druid/sql/dialect/oracle/parser/OracleStatementParser.java

@@ -104,7 +104,7 @@ public class OracleStatementParser extends SQLStatementParser {
         }
     }
 
-    public void parseStatementList(List<SQLStatement> statementList, int max) {
+    public void parseStatementList(List<SQLStatement> statementList, int max, SQLStatement parent) {
         for (;;) {
             if (max != -1) {
                 if (statementList.size() >= max) {
@@ -459,6 +459,10 @@ public class OracleStatementParser extends SQLStatementParser {
                 continue;
             }
 
+            if (lexer.token() == Token.ELSIF && parent instanceof SQLIfStatement) {
+                break;
+            }
+
             throw new ParserException("TODO : " + lexer.token() + " " + lexer.stringVal());
         }
     }
@@ -472,7 +476,20 @@ public class OracleStatementParser extends SQLStatementParser {
 
         accept(Token.THEN);
 
-        this.parseStatementList(stmt.getStatements());
+        this.parseStatementList(stmt.getStatements(), -1, stmt);
+
+        while (lexer.token() == Token.ELSIF) {
+            lexer.nextToken();
+
+            SQLIfStatement.ElseIf elseIf = new SQLIfStatement.ElseIf();
+
+            elseIf.setCondition(this.exprParser.expr());
+
+            accept(Token.THEN);
+            this.parseStatementList(elseIf.getStatements(), -1, stmt);
+
+            stmt.getElseIfList().add(elseIf);
+        }
 
         while (lexer.token() == Token.ELSE) {
             lexer.nextToken();

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

@@ -80,6 +80,10 @@ public class SQLStatementParser extends SQLParser {
     }
 
     public void parseStatementList(List<SQLStatement> statementList, int max) {
+        parseStatementList(statementList, max, null);
+    }
+
+    public void parseStatementList(List<SQLStatement> statementList, int max, SQLStatement parent) {
         for (;;) {
             if (max != -1) {
                 if (statementList.size() >= max) {

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

@@ -95,7 +95,8 @@ public enum Token {
     CASE("CASE"), 
     WHEN("WHEN"), 
     THEN("THEN"), 
-    ELSE("ELSE"), 
+    ELSE("ELSE"),
+    ELSIF("ELSIF"),
     END("END"), 
     EXISTS("EXISTS"), 
     IN("IN"),