diff --git a/core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLMergeStatement.java b/core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLMergeStatement.java
index 946948ab19..a430e9596d 100644
--- a/core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLMergeStatement.java
+++ b/core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLMergeStatement.java
@@ -30,6 +30,7 @@ public class SQLMergeStatement extends SQLStatementImpl {
     private SQLExpr on;
     private MergeUpdateClause updateClause;
     private MergeInsertClause insertClause;
+    private boolean insertClauseFirst;
     private SQLErrorLoggingClause errorLoggingClause;
 
     public void accept0(SQLASTVisitor visitor) {
@@ -107,6 +108,14 @@ public List<SQLHint> getHints() {
         return hints;
     }
 
+    public boolean isInsertClauseFirst() {
+        return insertClauseFirst;
+    }
+
+    public void setInsertClauseFirst(boolean insertClauseFirst) {
+        this.insertClauseFirst = insertClauseFirst;
+    }
+
     public static class MergeUpdateClause extends SQLObjectImpl {
         private List<SQLUpdateSetItem> items = new ArrayList<SQLUpdateSetItem>();
         private SQLExpr where;
diff --git a/core/src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java b/core/src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java
index 84ff10d98a..958c03f6b8 100644
--- a/core/src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java
+++ b/core/src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java
@@ -5402,6 +5402,7 @@ public SQLStatement parseMerge() {
                 }
 
                 stmt.setInsertClause(insertClause);
+                stmt.setInsertClauseFirst(stmt.getUpdateClause() == null);
             }
 
             if (lexer.token == Token.WHEN) {
diff --git a/core/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java b/core/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
index edf418445c..d228ae3efc 100644
--- a/core/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
+++ b/core/src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java
@@ -7961,14 +7961,24 @@ public boolean visit(SQLMergeStatement x) {
         x.getOn().accept(this);
         print0(") ");
 
-        if (x.getUpdateClause() != null) {
-            println();
-            x.getUpdateClause().accept(this);
-        }
-
-        if (x.getInsertClause() != null) {
-            println();
-            x.getInsertClause().accept(this);
+        if (x.isInsertClauseFirst()) {
+            if (x.getInsertClause() != null) {
+                println();
+                x.getInsertClause().accept(this);
+            }
+            if (x.getUpdateClause() != null) {
+                println();
+                x.getUpdateClause().accept(this);
+            }
+        } else {
+            if (x.getUpdateClause() != null) {
+                println();
+                x.getUpdateClause().accept(this);
+            }
+            if (x.getInsertClause() != null) {
+                println();
+                x.getInsertClause().accept(this);
+            }
         }
 
         if (x.getErrorLoggingClause() != null) {
diff --git a/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/OracleMergeTest10.java b/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/OracleMergeTest10.java
index 1e2bc3df9a..51ae1f270c 100644
--- a/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/OracleMergeTest10.java
+++ b/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/OracleMergeTest10.java
@@ -41,15 +41,15 @@ public void test_0() throws Exception {
         SQLMergeStatement mergeStatement = (SQLMergeStatement) stmtList.get(0);
         String result = SQLUtils.toOracleString(mergeStatement);
         Assert.assertEquals("MERGE INTO bonuses d\n" +
-                        "USING (\n" +
-                        "\tSELECT employee_id.*\n" +
-                        "\tFROM employees\n" +
-                        ") s ON (employee_id = a) \n" +
-                        "WHEN MATCHED THEN UPDATE SET d.bonus = bonus\n" +
-                        "\tDELETE WHERE salary > 8000\n" +
-                        "WHEN NOT MATCHED THEN INSERT (d.employee_id, d.bonus) VALUES (s.employee_id, s.salary)\n" +
-                        "\tWHERE s.salary <= 8000",
-                result);
+                "USING (\n" +
+                "\tSELECT employee_id.*\n" +
+                "\tFROM employees\n" +
+                ") s ON (employee_id = a) \n" +
+                "WHEN NOT MATCHED THEN INSERT (d.employee_id, d.bonus) VALUES (s.employee_id, s.salary)\n" +
+                "\tWHERE s.salary <= 8000\n" +
+                "WHEN MATCHED THEN UPDATE SET d.bonus = bonus\n" +
+                "\tDELETE WHERE salary > 8000",
+            result);
         // Assert.assertTrue(visitor.getColumns().contains(new TableStat.Column("employees", "employee_id")));
         // Assert.assertTrue(visitor.getColumns().contains(new TableStat.Column("employees", "salary")));
         // Assert.assertTrue(visitor.getColumns().contains(new TableStat.Column("employees", "department_id")));
diff --git a/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/issues/Issue5631.java b/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/issues/Issue5631.java
new file mode 100644
index 0000000000..eb841762b8
--- /dev/null
+++ b/core/src/test/java/com/alibaba/druid/bvt/sql/oracle/issues/Issue5631.java
@@ -0,0 +1,48 @@
+package com.alibaba.druid.bvt.sql.oracle.issues;
+
+import com.alibaba.druid.DbType;
+import com.alibaba.druid.bvt.sql.mysql.issues.Issue5421;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.parser.SQLParserUtils;
+import com.alibaba.druid.sql.parser.SQLStatementParser;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * 验证 Oracle merge sql的顺序问题
+ *
+ * @author lizongbo
+ * @see <a href="https://github.com/alibaba/druid/issues/5631">Issue来源</a>
+ */
+public class Issue5631 {
+
+    @Test
+    public void test_merge_into() throws Exception {
+        for (DbType dbType : new DbType[]{DbType.oracle}) {
+            for (String sql : new String[]{
+                "MERGE INTO  target_table\n"
+                    + "USING source_table ON (target_table.id = source_table.id)\n"
+                    + "WHEN NOT MATCHED THEN INSERT (id, column1) VALUES (source_table.id, source_table.column1)\n"
+                    + "WHEN MATCHED THEN UPDATE SET target_table.column1 = source_table.column1",
+                "MERGE INTO  target_table\n"
+                    + "USING source_table ON (target_table.id = source_table.id)\n"
+                    + "WHEN MATCHED THEN UPDATE SET target_table.column1 = source_table.column1\n"
+                    + "WHEN NOT MATCHED THEN INSERT (id, column1) VALUES (source_table.id, source_table.column1)",
+            }) {
+                SQLStatementParser parser = SQLParserUtils.createSQLStatementParser(sql, dbType);
+                SQLStatement statement = parser.parseStatement();
+                System.out.println(dbType + "原始的sql===" + sql);
+                System.out.println(dbType + "原始sql归一化===" + Issue5421.normalizeSql(sql));
+                String newSql = statement.toString();
+                System.out.println(dbType + "初次解析生成的sql===" + newSql);
+                System.out.println(dbType + "初次解析生成的sql归一化===" + Issue5421.normalizeSql(newSql));
+                parser = SQLParserUtils.createSQLStatementParser(newSql, dbType);
+                statement = parser.parseStatement();
+                System.out.println(dbType + "重新解析sql归一化===" + Issue5421.normalizeSql(statement.toString()));
+                assertTrue(Issue5421.normalizeSql(sql).equalsIgnoreCase(Issue5421.normalizeSql(statement.toString())));
+            }
+        }
+    }
+}
diff --git a/core/src/test/java/com/alibaba/druid/bvt/sql/postgresql/PGMergeIntoTest0.java b/core/src/test/java/com/alibaba/druid/bvt/sql/postgresql/PGMergeIntoTest0.java
index c89cde63f2..a23b14c305 100644
--- a/core/src/test/java/com/alibaba/druid/bvt/sql/postgresql/PGMergeIntoTest0.java
+++ b/core/src/test/java/com/alibaba/druid/bvt/sql/postgresql/PGMergeIntoTest0.java
@@ -39,12 +39,12 @@ public void test_0() throws Exception {
         SQLStatement stmt = statementList.get(0);
 
         assertEquals("MERGE INTO CustomerAccount CA\n" +
-                "USING (\n" +
-                "\tSELECT CustomerId, TransactionValue\n" +
-                "\tFROM RecentTransactions\n" +
-                ") T ON (CA.CustomerId = T.CustomerId) \n" +
-                "WHEN MATCHED THEN UPDATE SET Balance = Balance + TransactionValue\n" +
-                "WHEN NOT MATCHED THEN INSERT (CustomerId, Balance) VALUES (T.CustomerId, T.TransactionValue);", stmt.toString());
+            "USING (\n" +
+            "\tSELECT CustomerId, TransactionValue\n" +
+            "\tFROM RecentTransactions\n" +
+            ") T ON (CA.CustomerId = T.CustomerId) \n" +
+            "WHEN NOT MATCHED THEN INSERT (CustomerId, Balance) VALUES (T.CustomerId, T.TransactionValue)\n" +
+            "WHEN MATCHED THEN UPDATE SET Balance = Balance + TransactionValue;" , stmt.toString());
 
         assertEquals(1, statementList.size());