MyBatis Dynamic SQL (ii)

1. <if> (single condition)

2, <choose> <when> (multiple branch conditions)

3, <where> for intelligent processing where conditions, can be intelligent to add and remove conditions and

<select>

SELECT * FROM user

<where>

<if test= "UserName! = null" >

and userName like #{username}

</if>

<if test= "id!= null" >

and Id= #{id}

</if>

</where>

</select>

4, <set> processing update operation, you can intelligently remove or add the comma inside the set

<update>

Update user

<set>

<if test= "UserName! = null" > username=#{username},</if>

<if test= "password!= null" > Password=#{password},</if>

</set>

</update>

5. <trim> can automatically add prefixes and suffixes to SQL to reduce prefix characters or suffix characters

<update>

Update user

<trim prefix= "Set" suffixoverride= "," suffix= "where Id=#{id}" >

<if test= "Username!=null and username!=" >

Username=#{username},

</if>

<if test= "Password!=null and password!=" >

Password=#{password},

</if>

</trim>

</update>

6, Foreach Loop flag, mainly used for cyclic query conditions, circular update

Circular query Condition:

<select>

SELECT * FROM user

<where>

ID in

<foreach item= "Item" index= "index" collection= "list" open= "(" separator= "," close= ")" >

#{item}

</foreach>

</where>

</select>

Batch assignment:

<insert>

Insert into User (Username,password)

Values

<foreach item= "Item" index= "index" collection= "list" open= "" close= "" separator= "," >

(#{item.username},#{item.password})

<foreach>

</insert>

Explain:

An element that the item loops to

Index of an index loop

Collection of collection Loops

Start symbol for Open loop

Closing symbol for Close loop

MyBatis Dynamic SQL (ii)