04(04年今年多大)

  本篇文章为你整理了04(04年今年多大)的详细内容,包含有04年属什么生肖年 04年今年多大 04年属猴什么命 04a步兵战车 04,希望能帮助你了解 04。

  一、wapper介绍

  

Wrapper : 条件构造抽象类,最顶端父类

 

   AbstractWrapper : 用于查询条件封装,生成 sql 的 where 条件

   QueryWrapper : Entity 对象封装操作类,不是用lambda语法

   UpdateWrapper : Update 条件封装,用于Entity对象更新操作

   AbstractLambdaWrapper : Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。

   LambdaQueryWrapper :看名称也能明白就是用于Lambda语法使用的查询Wrapper

   LambdaUpdateWrapper : Lambda 更新封装Wrapper

  

 

  

@RunWith(SpringRunner.class)

 

  @SpringBootTest

  public class QueryWrapperTests {

   @Autowired

   private UserMapper userMapper;

  

 

  二、AbstractWrapper

  注意:以下条件构造器的方法入参中的 column 均表示数据库字段

  1、ge、gt、le、lt、isNull、isNotNull

  

@Test

 

  public void testDelete() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper

   .isNull("name")

   .ge("age", 12)

   .isNotNull("email");

   int result = userMapper.delete(queryWrapper);

   System.out.println("delete return count = " + result);

  

 

  SQL:UPDATE user SET deleted=1 WHERE deleted=0 AND name IS NULL AND age = ? AND email IS NOT NULL

  2、eq、ne

  注意:seletOne返回的是一条实体记录,当出现多条时会报错

  

@Test

 

  public void testSelectOne() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper.eq("name", "Tom");

   User user = userMapper.selectOne(queryWrapper);

   System.out.println(user);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name = ?

  3、between、notBetween

  包含大小边界

  

@Test

 

  public void testSelectCount() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper.between("age", 20, 30);

   Integer count = userMapper.selectCount(queryWrapper);

   System.out.println(count);

  

 

  SELECT COUNT(1) FROM user WHERE deleted=0 AND age BETWEEN ? AND ?

  4、allEq

  

@Test

 

  public void testSelectList() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   Map String, Object map = new HashMap ();

   map.put("id", 2);

   map.put("name", "Jack");

   map.put("age", 20);

   queryWrapper.allEq(map);

   List User users = userMapper.selectList(queryWrapper);

   users.forEach(System.out::println);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name = ? AND id = ? AND age = ?

  5、like、notLike、likeLeft、likeRight

  selectMaps返回Map集合列表

  

@Test

 

  public void testSelectMaps() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper

   .notLike("name", "e")

   .likeRight("email", "t");

   List Map String, Object maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表

   maps.forEach(System.out::println);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version
 

  FROM user WHERE deleted=0 AND name NOT LIKE ? AND email LIKE ?

  6、in、notIn、inSql、notinSql、exists、notExists

  in、notIn:

  notIn("age",{1,2,3})--- age not in (1,2,3)

  notIn("age", 1, 2, 3)--- age not in (1,2,3)
 

  inSql、notinSql:可以实现子查询

  例: inSql("age", "1,2,3,4,5,6")--- age in (1,2,3,4,5,6)

  例: inSql("id", "select id from table where id 3")--- id in (select id from table where id 3)

  

@Test

 

  public void testSelectObjs() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   //queryWrapper.in("id", 1, 2, 3);

   queryWrapper.inSql("id", "select id from user where id 3");

   List Object objects = userMapper.selectObjs(queryWrapper);//返回值是Object列表

   objects.forEach(System.out::println);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version
 

  FROM user WHERE deleted=0 AND id IN (select id from user where id 3)

  7、or、and

  注意:这里使用的是 UpdateWrapper
 

  不调用or则默认为使用 and 连

  

@Test

 

  public void testUpdate1() {

   //修改值

   User user = new User();

   user.setAge(99);

   user.setName("Andy");

   //修改条件

   UpdateWrapper User userUpdateWrapper = new UpdateWrapper ();

   userUpdateWrapper

   .like("name", "h")

   .or()

   .between("age", 20, 30);

   int result = userMapper.update(user, userUpdateWrapper);

   System.out.println(result);

  

 

  UPDATE user SET name=?, age=?, update_time=? WHERE deleted=0 AND name LIKE ? OR age BETWEEN ? AND ?

  8、嵌套or、嵌套and

  这里使用了lambda表达式,or中的表达式最后翻译成sql时会被加上圆括号

  

@Test

 

  public void testUpdate2() {

   //修改值

   User user = new User();

   user.setAge(99);

   user.setName("Andy");

   //修改条件

   UpdateWrapper User userUpdateWrapper = new UpdateWrapper ();

   userUpdateWrapper

   .like("name", "h")

   .or(i - i.eq("name", "李白").ne("age", 20));

   int result = userMapper.update(user, userUpdateWrapper);

   System.out.println(result);

  

 

  UPDATE user SET name=?, age=?, update_time=?
 

  WHERE deleted=0 AND name LIKE ?
 

  OR ( name = ? AND age ? )

  9、orderBy、orderByDesc、orderByAsc

  

@Test

 

  public void testSelectListOrderBy() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper.orderByDesc("id");

   List User users = userMapper.selectList(queryWrapper);

   users.forEach(System.out::println);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version
 

  FROM user WHERE deleted=0 ORDER BY id DESC

  10、last

  直接拼接到 sql 的最后
 

  注意:只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用

  

@Test

 

  public void testSelectListLast() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper.last("limit 1");

   List User users = userMapper.selectList(queryWrapper);

   users.forEach(System.out::println);

  

 

  SELECT id,name,age,email,create_time,update_time,deleted,version
 

  FROM user WHERE deleted=0 limit 1

  11、指定要查询的列

  

@Test

 

  public void testSelectListColumn() {

   QueryWrapper User queryWrapper = new QueryWrapper ();

   queryWrapper.select("id", "name", "age");

   List User users = userMapper.selectList(queryWrapper);

   users.forEach(System.out::println);

  

 

  SELECT id,name,age FROM user WHERE deleted=0

  12、set、setSql

  最终的sql会合并 user.setAge(),以及 userUpdateWrapper.set() 和 setSql() 中 的字段

  

@Test

 

  public void testUpdateSet() {

   //修改值

   User user = new User();

   user.setAge(99);

   //修改条件

   UpdateWrapper User userUpdateWrapper = new UpdateWrapper ();

   userUpdateWrapper

   .like("name", "h")

   .set("name", "老李头")//除了可以查询还可以使用set设置修改的字段

   .setSql(" email = 123@qq.com");//可以有子查询

   int result = userMapper.update(user, userUpdateWrapper);

  

 

  UPDATE user SET age=?, update_time=?, name=?, email = 123@qq.com WHERE deleted=0 AND name LIKE ?

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