[issues](https://gitee.com/best_handsome/mybatis-plus-join/issues/I3D5T7)

src/main/java/com/github/yulichang/toolkit/Constant.java

@@ -42,4 +42,18 @@ public interface Constant {
      */
     String INNER_JOIN = StringPool.SPACE + INNER + StringPool.SPACE + JOIN + StringPool.SPACE;
 
+    /**
+     * " t"
+     */
+    String SPACE_TABLE_ALIAS = StringPool.SPACE + Constant.TABLE_ALIAS;
+
+    /**
+     * " ON t"
+     */
+    String ON_TABLE_ALIAS = Constant.ON + Constant.TABLE_ALIAS;
+
+    /**
+     * " = t"
+     */
+    String EQUALS_TABLE_ALIAS = Constant.EQUALS + Constant.TABLE_ALIAS;
 }

src/main/java/com/github/yulichang/wrapper/MPJAbstractLambdaWrapper.java

@@ -1,7 +1,6 @@
 package com.github.yulichang.wrapper;
 
 import com.baomidou.mybatisplus.core.toolkit.StringPool;
-import com.baomidou.mybatisplus.core.toolkit.support.ColumnCache;
 import com.baomidou.mybatisplus.core.toolkit.support.SFunction;
 import com.github.yulichang.toolkit.Constant;
 import com.github.yulichang.toolkit.LambdaUtils;
@@ -20,29 +19,16 @@ import static java.util.stream.Collectors.joining;
 public abstract class MPJAbstractLambdaWrapper<T, Children extends MPJAbstractLambdaWrapper<T, Children>>
         extends MPJAbstractWrapper<T, Children> {
 
-    private Map<String, ColumnCache> columnMap = null;
-    private boolean initColumnMap = false;
-
     /**
      * 关联的表
      */
     protected final Map<Class<?>, Integer> subTable = new HashMap<>();
 
-    @SuppressWarnings("unchecked")
-    protected <X> String columnsToString(SFunction<X, ?>... columns) {
-        return columnsToString(true, columns);
-    }
-
     @Override
     protected <X> String columnToString(X column) {
         return columnToString((SFunction<?, ?>) column, true);
     }
 
-    @SuppressWarnings("unchecked")
-    protected <X> String columnsToString(boolean onlyColumn, SFunction<X, ?>... columns) {
-        return Arrays.stream(columns).map(i -> columnToString(i, onlyColumn)).collect(joining(StringPool.COMMA));
-    }
-
     @Override
     protected <X> String columnsToString(X... columns) {
         return Arrays.stream(columns).map(i -> columnToString((SFunction<?, ?>) i, true)).collect(joining(StringPool.COMMA));

src/main/java/com/github/yulichang/wrapper/MPJJoinLambdaQueryWrapper.java

@@ -133,12 +133,26 @@ public class MPJJoinLambdaQueryWrapper<T> extends MPJAbstractLambdaWrapper<T, MP
 
 
     public final <S, X> MPJJoinLambdaQueryWrapper<T> selectAs(SFunction<S, ?> columns, SFunction<X, ?> alias) {
+        return selectAs(true, columns, LambdaUtils.getName(alias));
+    }
+
+    /**
+     * @since 1.1.3
+     */
+    public final <S> MPJJoinLambdaQueryWrapper<T> selectAs(SFunction<S, ?> columns, String alias) {
         return selectAs(true, columns, alias);
     }
 
-    public final <S, X> MPJJoinLambdaQueryWrapper<T> selectAs(boolean condition, SFunction<S, ?> columns, SFunction<X, ?> alias) {
+    public final <S, X> MPJJoinLambdaQueryWrapper<T> selectAs(boolean condition, SFunction<S, ?> columns, SFunction alias) {
+        return selectAs(condition, columns, LambdaUtils.getName(alias));
+    }
+
+    /**
+     * @since 1.1.3
+     */
+    public final <S, X> MPJJoinLambdaQueryWrapper<T> selectAs(boolean condition, SFunction<S, ?> columns, String alias) {
         if (condition) {
-            selectColumns.add(new SelectColumn(LambdaUtils.getEntityClass(columns), LambdaUtils.getColumn(columns), LambdaUtils.getName(alias)));
+            selectColumns.add(new SelectColumn(LambdaUtils.getEntityClass(columns), LambdaUtils.getColumn(columns), alias));
         }
         return typedThis;
     }
@@ -160,7 +174,6 @@ public class MPJJoinLambdaQueryWrapper<T> extends MPJAbstractLambdaWrapper<T, MP
         return typedThis;
     }
 
-
     @Override
     public String getSqlSelect() {
         if (StringUtils.isBlank(sqlSelect.getStringValue())) {
@@ -203,24 +216,18 @@ public class MPJJoinLambdaQueryWrapper<T> extends MPJAbstractLambdaWrapper<T, MP
         if (condition) {
             subTable.put(clazz, tableIndex);
             TableInfo leftInfo = TableInfoHelper.getTableInfo(clazz);
-
             StringBuilder sb = new StringBuilder(keyWord)
                     .append(leftInfo.getTableName())
-                    .append(StringPool.SPACE)
+                    .append(Constant.SPACE_TABLE_ALIAS)
-                    .append(Constant.TABLE_ALIAS)
                     .append(tableIndex)
-                    .append(StringPool.SPACE)
+                    .append(Constant.ON_TABLE_ALIAS)
-                    .append(Constant.ON)
-                    .append(Constant.TABLE_ALIAS)
                     .append(tableIndex)
                     .append(StringPool.DOT)
                     .append(LambdaUtils.getColumn(left))
-                    .append(Constant.EQUALS)
+                    .append(Constant.EQUALS_TABLE_ALIAS)
-                    .append(Constant.TABLE_ALIAS)
                     .append(getDefault(subTable.get(LambdaUtils.getEntityClass(right))))
                     .append(StringPool.DOT)
                     .append(LambdaUtils.getColumn(right));
-
             tableIndex++;
             if (StringUtils.isBlank(from.getStringValue())) {
                 from.setStringValue(sb.toString());
@@ -231,7 +238,6 @@ public class MPJJoinLambdaQueryWrapper<T> extends MPJAbstractLambdaWrapper<T, MP
         return typedThis;
     }
 
-
     /**
      * select字段
      */