From 4aa76995d4a6b3e49f10c2fc037cfd04f702c3bc Mon Sep 17 00:00:00 2001
From: farukonfly <farukonfly@outlook.com>
Date: Mon, 4 Dec 2023 21:45:52 +0800
Subject: [PATCH] =?UTF-8?q?fix:DB2=20V10.5=20=E4=B8=8D=E6=94=AF=E6=8C=81Nu?=
 =?UTF-8?q?lls=20First|Nulls=20Last=20=E8=AF=AD=E6=B3=95=EF=BC=8C=E9=80=9A?=
 =?UTF-8?q?=E8=BF=87=E6=8A=8A=E8=AF=A5=E8=AF=AD=E6=B3=95=E9=87=8D=E5=86=99?=
 =?UTF-8?q?=E4=B8=BAcase=20when=E8=A7=A3=E5=86=B3?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../core/dialect/impl/DB2105Dialect.java      | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/mybatis-flex-core/src/main/java/com/mybatisflex/core/dialect/impl/DB2105Dialect.java b/mybatis-flex-core/src/main/java/com/mybatisflex/core/dialect/impl/DB2105Dialect.java
index 4f9ca73d..71ce16de 100644
--- a/mybatis-flex-core/src/main/java/com/mybatisflex/core/dialect/impl/DB2105Dialect.java
+++ b/mybatis-flex-core/src/main/java/com/mybatisflex/core/dialect/impl/DB2105Dialect.java
@@ -1,7 +1,18 @@
 package com.mybatisflex.core.dialect.impl;
 
+import static com.mybatisflex.core.constant.SqlConsts.DELIMITER;
+import static com.mybatisflex.core.constant.SqlConsts.NULLS_FIRST;
+import static com.mybatisflex.core.constant.SqlConsts.NULLS_LAST;
+import static com.mybatisflex.core.constant.SqlConsts.ORDER_BY;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 import com.mybatisflex.core.dialect.KeywordWrap;
 import com.mybatisflex.core.dialect.LimitOffsetProcessor;
+import com.mybatisflex.core.query.CPI;
+import com.mybatisflex.core.query.QueryOrderBy;
+import com.mybatisflex.core.query.QueryTable;
+import com.mybatisflex.core.query.QueryWrapper;
 
 public class DB2105Dialect extends CommonsDialectImpl {
       //TODO: 根据DatabaseMetaData获取数据库厂商名和版本号
@@ -13,6 +24,41 @@ public class DB2105Dialect extends CommonsDialectImpl {
         super(keywordWrap, limitOffsetProcessor);
     }
 
+ @Override
+    protected void buildOrderBySql(StringBuilder sqlBuilder, QueryWrapper queryWrapper, List<QueryTable> queryTables) {
+        List<QueryOrderBy> orderBys = CPI.getOrderBys(queryWrapper);
+        if (orderBys != null && !orderBys.isEmpty()) {
+            sqlBuilder.append(ORDER_BY);
+            int index = 0;
+            for (QueryOrderBy orderBy : orderBys) {
+                String orderBySql = orderBy.toSql(queryTables, this);
+                orderBySql = convertOderbySqlForDB2105(orderBySql);  // 转换SQL语句
+                sqlBuilder.append(orderBySql);
+                if (index != orderBys.size() - 1) {
+                    sqlBuilder.append(DELIMITER);
+                }
+                index++;
+            }
+        }
+    }
+
+    private  String convertOderbySqlForDB2105(String sql) {
+        Pattern pattern = Pattern.compile("(\\S+)\\s+(\\S+)\\s+("+NULLS_FIRST.trim()+"|"+NULLS_LAST.trim()+")");
+        Matcher matcher = pattern.matcher(sql);
+        if (matcher.find()) {
+            String column = matcher.group(1);
+            String orderType = matcher.group(2);
+            String nullOrder = matcher.group(3);
+            if (NULLS_FIRST.trim().equals(nullOrder)) {
+                sql = "CASE WHEN " + column + " IS NULL THEN 0 ELSE 1 END, " + column+" "+orderType;
+            } else if (NULLS_LAST.trim().equals(nullOrder)) {
+                sql = "CASE WHEN " + column + " IS NULL THEN 1 ELSE 0 END, " + column+" "+orderType;
+            }
+        }
+        return sql;
+    }
+
+
     public interface DB2105LimitOffsetProcessor {
         LimitOffsetProcessor DB2105 = (dialect, sql, queryWrapper, limitRows, limitOffset) -> {
             StringBuilder limitSqlFragment = new StringBuilder(