diff --git a/README.md b/README.md
index 943eabf..6cc2e53 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@
 
 使用方法：
 
-+ 在项目中放置jar包的地方把seq-1.5.2.jar、seq-1.5.2-sources.jar、seq-1.5.2-pom.xml复制过去
++ 在项目中放置jar包的地方把seq-1.6.2.jar、seq-1.6.2-sources.jar、seq-1.6.2-pom.xml复制过去
 + 在pom.xml中增加以下内容，然后执行maven命令：mvn clean
 
 ```xml
@@ -18,7 +18,7 @@
         <dependency>
             <groupId>com.yanghuanglin</groupId>
             <artifactId>seq</artifactId>
-            <version>1.5.2</version>
+            <version>1.6.2</version>
             <exclusions>
                 <!-- 如若你项目中有引用spring-jdbc，则需要排除seq的jdbc依赖 -->
                 <exclusion>
@@ -50,13 +50,13 @@
                         </goals>
                         <configuration>
                             <!-- ${project.basedir}表示当前项目的根目录 -->
-                            <file>${project.basedir}/lib/seq-1.5.2.jar</file>
-                            <pomFile>${project.basedir}/lib/seq-1.5.2-pom.xml</pomFile>
-                            <sources>${project.basedir}/lib/seq-1.5.2-sources.jar</sources>
+                            <file>${project.basedir}/lib/seq-1.6.2.jar</file>
+                            <pomFile>${project.basedir}/lib/seq-1.6.2-pom.xml</pomFile>
+                            <sources>${project.basedir}/lib/seq-1.6.2-sources.jar</sources>
                             <repositoryLayout>default</repositoryLayout>
                             <groupId>com.yanghuanglin</groupId>
                             <artifactId>seq</artifactId>
-                            <version>1.5.2</version>
+                            <version>1.6.2</version>
                             <packaging>jar</packaging>
                             <generatePom>true</generatePom>
                         </configuration>
@@ -478,6 +478,20 @@ public interface Generator {
      */
     void release(Date begin, Date end);
 
+    /**
+     * 释放从开始时间开始，到现在时间之间未使用的序号。结束时间为方法执行时的时间
+     *
+     * @param begin 开始时间
+     */
+    void releaseAfter(Date begin);
+
+    /**
+     * 释放结束时间以前的序号
+     *
+     * @param end 结束时间
+     */
+    void releaseBefore(Date end);
+
     /**
      * 释放指定序号。一般用于业务对象删除后，对应序号需要回收使用时。
      *
@@ -494,5 +508,20 @@ public interface Generator {
      * 清空指定时间段内闲置序号和未锁定序号
      */
     void clear(Date begin, Date end);
+
+    /**
+     * 清空从开始时间到限制时间之间闲置序号和未锁定序号，结束时间为方法执行时的时间
+     *
+     * @param begin 开始时间
+     */
+    void clearAfter(Date begin);
+
+    /**
+     * 清空结束时间之前的限制序号和未锁定序号
+     *
+     * @param end 结束时间
+     */
+    void clearBefore(Date end);
 }
+
 ```
\ No newline at end of file
diff --git a/pom.xml b/pom.xml
index 5cf34b9..48eef53 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,7 +4,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.yanghuanglin</groupId>
     <artifactId>seq</artifactId>
-    <version>1.5.2</version>
+    <version>1.6.2</version>
     <name>seq</name>
     <description>seq</description>
     <properties>
diff --git a/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnlockDaoImpl.java b/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnlockDaoImpl.java
index c5445bf..c10a932 100644
--- a/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnlockDaoImpl.java
+++ b/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnlockDaoImpl.java
@@ -48,9 +48,22 @@ public class SequencesUnlockDaoImpl implements SequencesUnlockDao {
 
     @Override
     public List<SequencesUnlock> listByDate(Date begin, Date end) {
-        String sql = "select * from `%s_unlock` where `%s`>=? and `%s`<=?";
-        sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
-        return this.jdbcTemplate.query(sql, rowMapper(), begin, end);
+        String sql;
+        if (begin != null && end != null) {
+            sql = "select * from `%s_unlock` where `%s`>=? and `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.query(sql, rowMapper(), begin, end);
+        } else if (begin != null) {
+            sql = "select * from `%s_unlock` where `%s`>=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.query(sql, rowMapper(), begin);
+        } else if (end != null) {
+            sql = "select * from `%s_unlock` where `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.query(sql, rowMapper(), end);
+        } else {
+            return listAll();
+        }
     }
 
     @Override
@@ -63,10 +76,22 @@ public class SequencesUnlockDaoImpl implements SequencesUnlockDao {
 
     @Override
     public boolean deleteByDate(Date begin, Date end) {
-        String sql = "delete from `%s_unlock` where `%s`>=? and `%s`<=?";
-        sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
-        int result = this.jdbcTemplate.update(sql, begin, end);
-        return result != 0;
+        String sql;
+        if (begin != null && end != null) {
+            sql = "delete from `%s_unlock` where `%s`>=? and `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, begin, end) != 0;
+        } else if (begin != null) {
+            sql = "delete from `%s_unlock` where `%s`>=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, begin) != 0;
+        } else if (end != null) {
+            sql = "delete from `%s_unlock` where `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, end) != 0;
+        } else {
+            return deleteAll();
+        }
     }
 
     @Override
diff --git a/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnusedDaoImpl.java b/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnusedDaoImpl.java
index 67d5184..fc0de5e 100644
--- a/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnusedDaoImpl.java
+++ b/src/main/java/com/yanghuanglin/seq/dao/impl/SequencesUnusedDaoImpl.java
@@ -118,10 +118,22 @@ public class SequencesUnusedDaoImpl implements SequencesUnusedDao {
 
     @Override
     public boolean deleteByDate(Date begin, Date end) {
-        String sql = "delete from `%s_unused` where `%s`>=? and `%s`<=?";
-        sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
-        int result = this.jdbcTemplate.update(sql, begin, end);
-        return result != 0;
+        String sql;
+        if (begin != null && end != null) {
+            sql = "delete from `%s_unused` where `%s`>=? and `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, begin, end) != 0;
+        } else if (begin != null) {
+            sql = "delete from `%s_unused` where `%s`>=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, begin) != 0;
+        } else if (end != null) {
+            sql = "delete from `%s_unused` where `%s`<=?";
+            sql = String.format(sql, tableConfig.getTable(), tableConfig.getCreateTimeColumn());
+            return this.jdbcTemplate.update(sql, end) != 0;
+        } else {
+            return deleteAll();
+        }
     }
 
     private RowMapper<SequencesUnused> rowMapper() {
diff --git a/src/main/java/com/yanghuanglin/seq/generator/Generator.java b/src/main/java/com/yanghuanglin/seq/generator/Generator.java
index ff24fb9..fd1c2a7 100644
--- a/src/main/java/com/yanghuanglin/seq/generator/Generator.java
+++ b/src/main/java/com/yanghuanglin/seq/generator/Generator.java
@@ -184,6 +184,20 @@ public interface Generator {
      */
     void release(Date begin, Date end);
 
+    /**
+     * 释放从开始时间开始，到现在时间之间未使用的序号。结束时间为方法执行时的时间
+     *
+     * @param begin 开始时间
+     */
+    void releaseAfter(Date begin);
+
+    /**
+     * 释放结束时间以前的序号
+     *
+     * @param end 结束时间
+     */
+    void releaseBefore(Date end);
+
     /**
      * 释放指定序号。一般用于业务对象删除后，对应序号需要回收使用时。
      *
@@ -200,4 +214,18 @@ public interface Generator {
      * 清空指定时间段内闲置序号和未锁定序号
      */
     void clear(Date begin, Date end);
+
+    /**
+     * 清空从开始时间到限制时间之间闲置序号和未锁定序号，结束时间为方法执行时的时间
+     *
+     * @param begin 开始时间
+     */
+    void clearAfter(Date begin);
+
+    /**
+     * 清空结束时间之前的限制序号和未锁定序号
+     *
+     * @param end 结束时间
+     */
+    void clearBefore(Date end);
 }
diff --git a/src/main/java/com/yanghuanglin/seq/generator/impl/SequencesGenerator.java b/src/main/java/com/yanghuanglin/seq/generator/impl/SequencesGenerator.java
index e9e8ea0..1031d10 100644
--- a/src/main/java/com/yanghuanglin/seq/generator/impl/SequencesGenerator.java
+++ b/src/main/java/com/yanghuanglin/seq/generator/impl/SequencesGenerator.java
@@ -50,7 +50,7 @@ public class SequencesGenerator implements Generator {
      *
      * @param autoCreate 是否自动创建
      */
-    private void createTable(Boolean autoCreate) {
+    private synchronized void createTable(Boolean autoCreate) {
         if (!autoCreate)
             return;
         this.sequencesDao.createTable();
@@ -274,6 +274,16 @@ public class SequencesGenerator implements Generator {
         sequencesUnlockDao.deleteByDate(begin, end);
     }
 
+    @Override
+    public synchronized void releaseAfter(Date begin) {
+        release(begin, null);
+    }
+
+    @Override
+    public synchronized void releaseBefore(Date end) {
+        release(null, end);
+    }
+
     @Override
     public synchronized void release(Sequences sequences) {
         if (sequences == null)
@@ -283,14 +293,24 @@ public class SequencesGenerator implements Generator {
     }
 
     @Override
-    public void clear() {
+    public synchronized void clear() {
         sequencesUnlockDao.deleteAll();
         sequencesUnusedDao.deleteAll();
     }
 
     @Override
-    public void clear(Date begin, Date end) {
+    public synchronized void clear(Date begin, Date end) {
         sequencesUnlockDao.deleteByDate(begin, end);
         sequencesUnusedDao.deleteByDate(begin, end);
     }
+
+    @Override
+    public synchronized void clearAfter(Date begin) {
+        clear(begin, null);
+    }
+
+    @Override
+    public synchronized void clearBefore(Date end) {
+        clear(null, end);
+    }
 }