diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtAbstractWrapper.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtAbstractWrapper.java
index 4bf7235..2c0f733 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtAbstractWrapper.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtAbstractWrapper.java
@@ -64,7 +64,7 @@ public abstract class KtAbstractWrapper<T, Children extends KtAbstractWrapper<T,
      * 其他
      */
     /* mybatis plus 3.4.3新增 这个时wrapper的别名 不是MPJ的别名 */
-    protected SharedString paramAlias;
+    protected SharedString paramAlias = new SharedString(null);
     protected SharedString lastSql;
     /**
      * SQL注释
@@ -607,9 +607,10 @@ public abstract class KtAbstractWrapper<T, Children extends KtAbstractWrapper<T,
         paramNameSeq.set(0);
         paramNameValuePairs.clear();
         expression.clear();
-        lastSql.toEmpty();
-        sqlComment.toEmpty();
-        sqlFirst.toEmpty();
+        paramAlias.toNull();
+        if (Objects.nonNull(lastSql)) lastSql.toEmpty();
+        if (Objects.nonNull(sqlComment)) sqlComment.toEmpty();
+        if (Objects.nonNull(sqlFirst)) sqlFirst.toEmpty();
         tableList.clear();
         entityClass = null;
         onWrappers.clear();
@@ -658,7 +659,7 @@ public abstract class KtAbstractWrapper<T, Children extends KtAbstractWrapper<T,
     }
 
     public String getParamAlias() {
-        return paramAlias == null ? Constants.WRAPPER : paramAlias.getStringValue();
+        return paramAlias.getStringValue() == null ? Constants.WRAPPER : paramAlias.getStringValue();
     }
 
     /**
@@ -669,9 +670,8 @@ public abstract class KtAbstractWrapper<T, Children extends KtAbstractWrapper<T,
      */
     public Children setParamAlias(String paramAlias) {
         Assert.notEmpty(paramAlias, "paramAlias can not be empty!");
-        Assert.isTrue(CollectionUtils.isEmpty(paramNameValuePairs), "Please call this method before working!");
-        Assert.isNull(this.paramAlias, "Please do not call the method repeatedly!");
-        this.paramAlias = new SharedString(paramAlias);
+        Assert.isNull(this.paramAlias.getStringValue(), "Please do not call the method repeatedly!");
+        this.paramAlias.setStringValue(paramAlias);
         return typedThis;
     }
 
diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtLambdaWrapper.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtLambdaWrapper.java
index 04f7d6d..96b800b 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtLambdaWrapper.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/kt/KtLambdaWrapper.java
@@ -125,7 +125,7 @@ public class KtLambdaWrapper<T> extends KtAbstractLambdaWrapper<T, KtLambdaWrapp
      * 不建议直接 new 该实例，使用 JoinWrappers.lambda(UserDO.class)
      */
     KtLambdaWrapper(T entity, Class<T> entityClass, SharedString sqlSelect, AtomicInteger paramNameSeq,
-                    Map<String, Object> paramNameValuePairs, MergeSegments mergeSegments,
+                    Map<String, Object> paramNameValuePairs, MergeSegments mergeSegments, SharedString paramAlias,
                     SharedString lastSql, SharedString sqlComment, SharedString sqlFirst,
                     TableList tableList, Integer index, String keyWord, Class<?> joinClass, String tableName) {
         super.setEntity(entity);
@@ -134,6 +134,7 @@ public class KtLambdaWrapper<T> extends KtAbstractLambdaWrapper<T, KtLambdaWrapp
         this.paramNameValuePairs = paramNameValuePairs;
         this.expression = mergeSegments;
         this.sqlSelect = sqlSelect;
+        this.paramAlias = paramAlias;
         this.lastSql = lastSql;
         this.sqlComment = sqlComment;
         this.sqlFirst = sqlFirst;
@@ -207,7 +208,7 @@ public class KtLambdaWrapper<T> extends KtAbstractLambdaWrapper<T, KtLambdaWrapp
     @SuppressWarnings("DuplicatedCode")
     public KtLambdaWrapper<T> selectSub(Class<?> clazz, String st, Consumer<KtLambdaWrapper<?>> consumer, KProperty<?> alias) {
         KtLambdaWrapper<?> wrapper = new KtLambdaWrapper(null, clazz, SharedString.emptyString(), paramNameSeq, paramNameValuePairs,
-                new MergeSegments(), SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
+                new MergeSegments(), SharedString.emptyString(), this.paramAlias, SharedString.emptyString(), SharedString.emptyString(),
                 new TableList(), null, null, null, null) {
         };
         wrapper.tableList.setAlias(st);
@@ -348,7 +349,7 @@ public class KtLambdaWrapper<T> extends KtAbstractLambdaWrapper<T, KtLambdaWrapp
     @Override
     protected KtLambdaWrapper<T> instance(Integer index, String keyWord, Class<?> joinClass, String tableName) {
         return new KtLambdaWrapper<>(getEntity(), getEntityClass(), null, paramNameSeq, paramNameValuePairs,
-                new MergeSegments(), SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
+                new MergeSegments(), SharedString.emptyString(), this.paramAlias, SharedString.emptyString(), SharedString.emptyString(),
                 this.tableList, index, keyWord, joinClass, tableName);
     }
 
@@ -356,7 +357,8 @@ public class KtLambdaWrapper<T> extends KtAbstractLambdaWrapper<T, KtLambdaWrapp
     public void clear() {
         super.clear();
         selectDistinct = false;
-        sqlSelect.toNull();
+        sqlSelect.toEmpty();
+        if (Objects.nonNull(unionSql)) unionSql.toEmpty();
         selectColumns.clear();
         wrapperIndex = new AtomicInteger(0);
         wrapperMap.clear();
diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractLambdaWrapper.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractLambdaWrapper.java
index d1dbc5d..38b5a75 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractLambdaWrapper.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractLambdaWrapper.java
@@ -23,6 +23,7 @@ import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
@@ -36,7 +37,7 @@ import static java.util.stream.Collectors.joining;
  *
  * @author yulichang
  */
-@SuppressWarnings({"DuplicatedCode", "unused", "LombokGetterMayBeUsed"})
+@SuppressWarnings({"DuplicatedCode", "unused"})
 public abstract class MPJAbstractLambdaWrapper<T, Children extends MPJAbstractLambdaWrapper<T, Children>>
         extends MPJAbstractWrapper<T, Children> implements QueryJoin<Children, T> {
 
@@ -455,7 +456,7 @@ public abstract class MPJAbstractLambdaWrapper<T, Children extends MPJAbstractLa
         this.dynamicTableName = false;
         this.tableFunc = null;
         this.logicDelType = ConfigProperties.logicDelType;
-        this.from.toNull();
+        this.from.toEmpty();
         this.hasAlias = false;
         this.keyWord = null;
         this.logicSql = true;
diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractWrapper.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractWrapper.java
index 5b8c5c5..768b9bb 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractWrapper.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJAbstractWrapper.java
@@ -59,7 +59,7 @@ public abstract class MPJAbstractWrapper<T, Children extends MPJAbstractWrapper<
      * 其他
      */
     /* mybatis plus 3.4.3新增 这个时wrapper的别名 不是MPJ的别名 */
-    protected SharedString paramAlias;
+    protected SharedString paramAlias = new SharedString(null);
     protected SharedString lastSql;
     /**
      * SQL注释
@@ -617,12 +617,13 @@ public abstract class MPJAbstractWrapper<T, Children extends MPJAbstractWrapper<
     @Override
     public void clear() {
         entity = null;
+        paramAlias.toNull();
         paramNameSeq.set(0);
         paramNameValuePairs.clear();
         expression.clear();
-        lastSql.toEmpty();
-        sqlComment.toEmpty();
-        sqlFirst.toEmpty();
+        if (Objects.nonNull(lastSql)) lastSql.toEmpty();
+        if (Objects.nonNull(sqlComment)) sqlComment.toEmpty();
+        if (Objects.nonNull(sqlFirst)) sqlFirst.toEmpty();
         tableList.clear();
         entityClass = null;
         onWrappers.clear();
@@ -671,7 +672,7 @@ public abstract class MPJAbstractWrapper<T, Children extends MPJAbstractWrapper<
     }
 
     public String getParamAlias() {
-        return paramAlias == null ? Constants.WRAPPER : paramAlias.getStringValue();
+        return paramAlias.getStringValue() == null ? Constants.WRAPPER : paramAlias.getStringValue();
     }
 
     /**
@@ -682,9 +683,8 @@ public abstract class MPJAbstractWrapper<T, Children extends MPJAbstractWrapper<
      */
     public Children setParamAlias(String paramAlias) {
         Assert.notEmpty(paramAlias, "paramAlias can not be empty!");
-        Assert.isTrue(CollectionUtils.isEmpty(paramNameValuePairs), "Please call this method before working!");
-        Assert.isNull(this.paramAlias, "Please do not call the method repeatedly!");
-        this.paramAlias = new SharedString(paramAlias);
+        Assert.isTrue(StringUtils.isBlank(this.paramAlias.getStringValue()), "Please do not call the method repeatedly!");
+        this.paramAlias.setStringValue(paramAlias);
         return typedThis;
     }
 
diff --git a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJLambdaWrapper.java b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJLambdaWrapper.java
index 16d171c..e3f8338 100644
--- a/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJLambdaWrapper.java
+++ b/mybatis-plus-join-core/src/main/java/com/github/yulichang/wrapper/MPJLambdaWrapper.java
@@ -123,7 +123,7 @@ public class MPJLambdaWrapper<T> extends MPJAbstractLambdaWrapper<T, MPJLambdaWr
      * 不建议直接 new 该实例，使用 JoinWrappers.lambda(UserDO.class)
      */
     MPJLambdaWrapper(T entity, Class<T> entityClass, SharedString sqlSelect, AtomicInteger paramNameSeq,
-                     Map<String, Object> paramNameValuePairs, MergeSegments mergeSegments,
+                     Map<String, Object> paramNameValuePairs, MergeSegments mergeSegments, SharedString paramAlias,
                      SharedString lastSql, SharedString sqlComment, SharedString sqlFirst,
                      TableList tableList, Integer index, String keyWord, Class<?> joinClass, String tableName) {
         super.setEntity(entity);
@@ -132,6 +132,7 @@ public class MPJLambdaWrapper<T> extends MPJAbstractLambdaWrapper<T, MPJLambdaWr
         this.paramNameValuePairs = paramNameValuePairs;
         this.expression = mergeSegments;
         this.sqlSelect = sqlSelect;
+        this.paramAlias = paramAlias;
         this.lastSql = lastSql;
         this.sqlComment = sqlComment;
         this.sqlFirst = sqlFirst;
@@ -207,7 +208,7 @@ public class MPJLambdaWrapper<T> extends MPJAbstractLambdaWrapper<T, MPJLambdaWr
     @SuppressWarnings("DuplicatedCode")
     public <E, F> MPJLambdaWrapper<T> selectSub(Class<E> clazz, String st, Consumer<MPJLambdaWrapper<E>> consumer, SFunction<F, ?> alias) {
         MPJLambdaWrapper<E> wrapper = new MPJLambdaWrapper<E>(null, clazz, SharedString.emptyString(), paramNameSeq, paramNameValuePairs,
-                new MergeSegments(), SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
+                new MergeSegments(), this.paramAlias, SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
                 new TableList(), null, null, null, null) {
         };
         wrapper.tableList.setAlias(st);
@@ -348,7 +349,7 @@ public class MPJLambdaWrapper<T> extends MPJAbstractLambdaWrapper<T, MPJLambdaWr
     @Override
     protected MPJLambdaWrapper<T> instance(Integer index, String keyWord, Class<?> joinClass, String tableName) {
         return new MPJLambdaWrapper<>(getEntity(), getEntityClass(), null, paramNameSeq, paramNameValuePairs,
-                new MergeSegments(), SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
+                new MergeSegments(), this.paramAlias, SharedString.emptyString(), SharedString.emptyString(), SharedString.emptyString(),
                 this.tableList, index, keyWord, joinClass, tableName);
     }
 
@@ -359,7 +360,8 @@ public class MPJLambdaWrapper<T> extends MPJAbstractLambdaWrapper<T, MPJLambdaWr
         sqlSelect.toNull();
         selectColumns.clear();
         wrapperIndex = new AtomicInteger(0);
-        wrapperMap.clear();
+        if (Objects.nonNull(wrapperMap)) wrapperMap.clear();
+        if (Objects.nonNull(unionSql)) unionSql.toEmpty();
         resultMapMybatisLabel.clear();
     }
 }
diff --git a/mybatis-plus-join-test/test-join/src/main/java/com/github/yulichang/test/join/entity/UserTTT.java b/mybatis-plus-join-test/test-join/src/main/java/com/github/yulichang/test/join/entity/UserTTT.java
deleted file mode 100644
index c7151c3..0000000
--- a/mybatis-plus-join-test/test-join/src/main/java/com/github/yulichang/test/join/entity/UserTTT.java
+++ /dev/null
@@ -1,4 +0,0 @@
-package com.github.yulichang.test.join.entity;
-
-public class UserTTT extends UserDO{
-}
diff --git a/mybatis-plus-join-test/test-join/src/test/java/com/github/yulichang/test/join/LambdaWrapperTest.java b/mybatis-plus-join-test/test-join/src/test/java/com/github/yulichang/test/join/LambdaWrapperTest.java
index e6082c8..1d72f7e 100644
--- a/mybatis-plus-join-test/test-join/src/test/java/com/github/yulichang/test/join/LambdaWrapperTest.java
+++ b/mybatis-plus-join-test/test-join/src/test/java/com/github/yulichang/test/join/LambdaWrapperTest.java
@@ -1094,11 +1094,14 @@ class LambdaWrapperTest {
                 .eq(UserDO::getId, 1);
         MPJLambdaWrapper<UserDO> wrapper1 = JoinWrappers.lambda(UserDO.class)
                 .selectAll(UserDO.class)
-                .eq(UserDO::getName, "张三 2");
+                .eq(UserDO::getName, "张三 2")
+                .and(w -> w.eq(UserDO::getName, "张三 2"));
         MPJLambdaWrapper<UserDO> wrapper2 = JoinWrappers.lambda(UserDO.class)
                 .selectAll(UserDO.class)
                 .eq(UserDO::getPid, 2);
         wrapper.union(wrapper1, wrapper2);
+
+        System.out.println(wrapper.getUnionSql());
         List<UserDO> list = wrapper.list();
 
         assert list.size() == 7;
diff --git a/mybatis-plus-join-test/test-kotlin/src/test/com/github/yulichang/test/kt/LambdaWrapperTest.kt b/mybatis-plus-join-test/test-kotlin/src/test/com/github/yulichang/test/kt/LambdaWrapperTest.kt
index e974a64..43b61de 100644
--- a/mybatis-plus-join-test/test-kotlin/src/test/com/github/yulichang/test/kt/LambdaWrapperTest.kt
+++ b/mybatis-plus-join-test/test-kotlin/src/test/com/github/yulichang/test/kt/LambdaWrapperTest.kt
@@ -1146,6 +1146,7 @@ class LambdaWrapperTest {
         val wrapper1: KtLambdaWrapper<UserDO> = KtWrappers.query(UserDO::class.java)
                 .selectAll(UserDO::class.java)
                 .eq(UserDO::name, "张三 2")
+                .and { a -> a.eq(UserDO::name, "张三 2") }
         val wrapper2: KtLambdaWrapper<UserDO> = KtWrappers.query(UserDO::class.java)
                 .selectAll(UserDO::class.java)
                 .eq(UserDO::pid, 2)