wapper介紹?

Wrapper ： 條件構造抽象類，最頂端父類

? ? AbstractWrapper ： 用于查詢條件封裝，生成 sql 的 where 條件

? ? ? ? QueryWrapper ： Entity 對象封裝操作類，不是用lambda語法

? ? ? ? UpdateWrapper ： Update 條件封裝，用于Entity對象更新操作

? ? AbstractLambdaWrapper ： Lambda 語法使用 Wrapper統一處理解析 lambda 獲取 column。

? ? ? ? LambdaQueryWrapper ：看名稱也能明白就是用于Lambda語法使用的查詢Wrapper

? ? ? ? LambdaUpdateWrapper ： Lambda 更新封裝Wrapper

@RunWith(SpringRunner.class) @SpringBootTest public class QueryWrapperTests {@Autowiredprivate UserMapper userMapper;}

AbstractWrapper

注意：以下條件構造器的方法入參中的?column?均表示數據庫字段

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

eq、ne

注意：seletOne返回的是一條實體記錄，當出現多條時會報錯

@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 = ??

between、notBetween

包含大小邊界

@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 ??

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 = ??

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 ??

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：可以實現子查詢

• 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)?

or、and

注意：這里使用的是?UpdateWrapper?

不調用or則默認為使用?and?連

@Test public void testUpdate1() {//修改值User user = new User();user.setAge(99);user.setName("Andy");//修改條件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 ?

嵌套or、嵌套and

這里使用了lambda表達式，or中的表達式最后翻譯成sql時會被加上圓括號

@Test public void testUpdate2() {//修改值User user = new User();user.setAge(99);user.setName("Andy");//修改條件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 <> ? )?

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 DE

last

直接拼接到 sql 的最后

注意：只能調用一次,多次調用以最后一次為準 有sql注入的風險,請謹慎使用

@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?

指定要查詢的列

@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?

set、setSql

最終的sql會合并 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);//修改條件UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();userUpdateWrapper.like("name", "h").set("name", "老李頭")//除了可以查詢還可以使用set設置修改的字段.setSql(" email = '123@qq.com'");//可以有子查詢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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