数据库教程:QueryWarpper的使用方法，MyBatics Plus的查询方法处理

目录

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# AbstractWrapper

# allEq

# eq

# ne

# gt

# ge

# lt

# le

# between

# notBetween

# like

# notLike

# likeLeft

# likeRight

# isNull

# isNotNull

# in

# notIn

# inSql

# notInSql

# groupBy

# orderByAsc

# orderByDesc

# orderBy

# having

# func

# or

# and

# nested

# apply

# last

# exists

# notExists

# QueryWrapper

# select

# UpdateWrapper

# set

# setSql

# lambda

MyBatics Plus官网

https://mp.baomidou.com/guide/#%E7%89%B9%E6%80%A7 

# AbstractWrapper

说明:

QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类
用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件
注意: entity 生成的 where 条件与 使用各个 api 生成的 where 条件没有任何关联行为

# allEq

 allEq(Map<R, V> params) allEq(Map<R, V> params, boolean null2IsNull) allEq(boolean condition, Map<R, V> params, boolean null2IsNull) 

• 全部eq(或个别isNull)

个别参数说明:

params : key为数据库字段名,value为字段值
null2IsNull : 为true则在map的value为null时调用 isNull 方法,为false时则忽略value为null的

• 例1: allEq({id:1,name:"老王",age:null})—>id = 1 and name = '老王' and age is null
• 例2: allEq({id:1,name:"老王",age:null}, false)—>id = 1 and name = '老王'

 allEq(BiPredicate<R, V> filter, Map<R, V> params) allEq(BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull) allEq(boolean condition, BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)  

个别参数说明:

filter : 过滤函数,是否允许字段传入比对条件中
params 与 null2IsNull : 同上

• 例1: allEq((k,v) -> k.indexOf("a") >= 0, {id:1,name:"老王",age:null})—>name = '老王' and age is null
• 例2: allEq((k,v) -> k.indexOf("a") >= 0, {id:1,name:"老王",age:null}, false)—>name = '老王'

# eq

 eq(R column, Object val) eq(boolean condition, R column, Object val) 

• 等于 =
• 例: eq("name", "老王")—>name = '老王'

# ne

 ne(R column, Object val) ne(boolean condition, R column, Object val) 

• 不等于 <>
• 例: ne("name", "老王")—>name <> '老王'

# gt

 gt(R column, Object val) gt(boolean condition, R column, Object val) 

• 大于 >
• 例: gt("age", 18)—>age > 18

# ge

 ge(R column, Object val) ge(boolean condition, R column, Object val) 

• 大于等于 >=
• 例: ge("age", 18)—>age >= 18

# lt

 lt(R column, Object val) lt(boolean condition, R column, Object val) 

• 小于 <
• 例: lt("age", 18)—>age < 18

# le

 le(R column, Object val) le(boolean condition, R column, Object val) 

• 小于等于 <=
• 例: le("age", 18)—>age <= 18

# between

 between(R column, Object val1, Object val2) between(boolean condition, R column, Object val1, Object val2) 

• BETWEEN 值1 AND 值2
• 例: between("age", 18, 30)—>age between 18 and 30

# notBetween

 notBetween(R column, Object val1, Object val2) notBetween(boolean condition, R column, Object val1, Object val2) 

• NOT BETWEEN 值1 AND 值2
• 例: notBetween("age", 18, 30)—>age not between 18 and 30

# like

 like(R column, Object val) like(boolean condition, R column, Object val) 

• LIKE ‘%值%’
• 例: like("name", "王")—>name like '%王%'

# notLike

 notLike(R column, Object val) notLike(boolean condition, R column, Object val) 

• NOT LIKE ‘%值%’
• 例: notLike("name", "王")—>name not like '%王%'

# likeLeft

 likeLeft(R column, Object val) likeLeft(boolean condition, R column, Object val) 

• LIKE ‘%值’
• 例: likeLeft("name", "王")—>name like '%王'

# likeRight

 likeRight(R column, Object val) likeRight(boolean condition, R column, Object val) 

• LIKE ‘值%’
• 例: likeRight("name", "王")—>name like '王%'

# isNull

 isNull(R column) isNull(boolean condition, R column) 

• 字段 IS NULL
• 例: isNull("name")—>name is null

# isNotNull

 isNotNull(R column) isNotNull(boolean condition, R column) 

• 字段 IS NOT NULL
• 例: isNotNull("name")—>name is not null

# in

 in(R column, Collection<?> value) in(boolean condition, R column, Collection<?> value) 

• 字段 IN (value.get(0), value.get(1), …)
• 例: in("age",{1,2,3})—>age in (1,2,3)

 in(R column, Object... values) in(boolean condition, R column, Object... values) 

• 字段 IN (v0, v1, …)
• 例: in("age", 1, 2, 3)—>age in (1,2,3)

# notIn

 notIn(R column, Collection<?> value) notIn(boolean condition, R column, Collection<?> value) 

• 字段 NOT IN (value.get(0), value.get(1), …)
• 例: notIn("age",{1,2,3})—>age not in (1,2,3)

 notIn(R column, Object... values) notIn(boolean condition, R column, Object... values) 

• 字段 NOT IN (v0, v1, …)
• 例: notIn("age", 1, 2, 3)—>age not in (1,2,3)

# inSql

 inSql(R column, String inValue) inSql(boolean condition, R column, String inValue) 

• 字段 IN ( sql语句 )
• 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)

# notInSql

 notInSql(R column, String inValue) notInSql(boolean condition, R column, String inValue) 

• 字段 NOT IN ( sql语句 )
• 例: notInSql("age", "1,2,3,4,5,6")—>age not in (1,2,3,4,5,6)
• 例: notInSql("id", "select id from table where id < 3")—>id not in (select id from table where id < 3)

# groupBy

 groupBy(R... columns) groupBy(boolean condition, R... columns) 

• 分组：GROUP BY 字段, …
• 例: groupBy("id", "name")—>group by id,name

# orderByAsc

 orderByAsc(R... columns) orderByAsc(boolean condition, R... columns) 

• 排序：ORDER BY 字段, … ASC
• 例: orderByAsc("id", "name")—>order by id ASC,name ASC

# orderByDesc

 orderByDesc(R... columns) orderByDesc(boolean condition, R... columns) 

• 排序：ORDER BY 字段, … DESC
• 例: orderByDesc("id", "name")—>order by id DESC,name DESC

# orderBy

 orderBy(boolean condition, boolean isAsc, R... columns) 

• 排序：ORDER BY 字段, …
• 例: orderBy(true, true, "id", "name")—>order by id ASC,name ASC

# having

 having(String sqlHaving, Object... params) having(boolean condition, String sqlHaving, Object... params) 

• HAVING ( sql语句 )
• 例: having("sum(age) > 10")—>having sum(age) > 10
• 例: having("sum(age) > {0}", 11)—>having sum(age) > 11

# func

 func(Consumer<Children> consumer) func(boolean condition, Consumer<Children> consumer) 

• func 方法(主要方便在出现if…else下调用不同方法能不断链)
• 例: func(i -> if(true) {i.eq("id", 1)} else {i.ne("id", 1)})

# or

 or() or(boolean condition) 

• 拼接 OR

注意事项:

主动调用or表示紧接着下一个方法不是用and连接!(不调用or则默认为使用and连接)

• 例: eq("id",1).or().eq("name","老王")—>id = 1 or name = '老王'

 or(Consumer<Param> consumer) or(boolean condition, Consumer<Param> consumer) 

• OR 嵌套
• 例: or(i -> i.eq("name", "李白").ne("status", "活着"))—>or (name = '李白' and status <> '活着')

# and

 and(Consumer<Param> consumer) and(boolean condition, Consumer<Param> consumer) 

• AND 嵌套
• 例: and(i -> i.eq("name", "李白").ne("status", "活着"))—>and (name = '李白' and status <> '活着')

# nested

 nested(Consumer<Param> consumer) nested(boolean condition, Consumer<Param> consumer) 

• 正常嵌套 不带 AND 或者 OR
• 例: nested(i -> i.eq("name", "李白").ne("status", "活着"))—>(name = '李白' and status <> '活着')

# apply

 apply(String applySql, Object... params) apply(boolean condition, String applySql, Object... params) 

• 拼接 sql

注意事项:

该方法可用于数据库函数 动态入参的params对应前面applySql内部的{index}部分.这样是不会有sql注入风险的,反之会有!

• 例: apply("id = 1")—>id = 1
• 例: apply("date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")—>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")
• 例: apply("date_format(dateColumn,'%Y-%m-%d') = {0}", "2008-08-08")—>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")

# last

 last(String lastSql) last(boolean condition, String lastSql) 

• 无视优化规则直接拼接到 sql 的最后

注意事项:

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

• 例: last("limit 1")

# exists

 exists(String existsSql) exists(boolean condition, String existsSql) 

• 拼接 EXISTS ( sql语句 )
• 例: exists("select id from table where age = 1")—>exists (select id from table where age = 1)

# notExists

 notExists(String notExistsSql) notExists(boolean condition, String notExistsSql) 

• 拼接 NOT EXISTS ( sql语句 )
• 例: notExists("select id from table where age = 1")—>not exists (select id from table where age = 1)

# QueryWrapper

说明:

继承自 AbstractWrapper ,自身的内部属性 entity 也用于生成 where 条件
及 LambdaQueryWrapper, 可以通过 new QueryWrapper().lambda() 方法获取

# select

 select(String... sqlSelect) select(Predicate<TableFieldInfo> predicate) select(Class<T> entityClass, Predicate<TableFieldInfo> predicate) 

• 设置查询字段

说明:

以上方分法为两类.
第二类方法为:过滤查询字段(主键除外),入参不包含 class 的调用前需要wrapper内的entity属性有值! 这两类方法重复调用以最后一次为准

• 例: select("id", "name", "age")
• 例: select(i -> i.getProperty().startsWith("test"))

# UpdateWrapper

说明:

继承自 AbstractWrapper ,自身的内部属性 entity 也用于生成 where 条件
及 LambdaUpdateWrapper, 可以通过 new UpdateWrapper().lambda() 方法获取!

# set

 set(String column, Object val) set(boolean condition, String column, Object val) 

• SQL SET 字段
• 例: set("name", "老李头")
• 例: set("name", "")—>数据库字段值变为空字符串
• 例: set("name", null)—>数据库字段值变为null

# setSql

 setSql(String sql) 

• 设置 SET 部分 SQL
• 例: setSql("name = '老李头'")

# lambda

• 获取 LambdaWrapper
  在QueryWrapper中是获取LambdaQueryWrapper
  在UpdateWrapper中是获取LambdaUpdateWrapper

数据库技术:QueryWarpper的使用方法，MyBatics Plus的查询方法处理地址：https://blog.csdn.net/qq_25580555/article/details/107385285

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