sql

This element can be used to define a reusable fragment of SQL code that can be included in other statements. It can be statically (during load phase) parametrized. Different property values can vary in include instances. For example:

<sql id="userColumns"> ${alias}.id,${alias}.username,${alias}.password </sql>

The SQL fragment can then be included in another statement, for example:

<select id="selectUsers" resultType="map">
  select
    <include refid="userColumns"><property name="alias" value="t1"/></include>,
    <include refid="userColumns"><property name="alias" value="t2"/></include>
  from some_table t1
    cross join some_table t2
</select>

Property value can be also used in include refid attribute or property values inside include clause, for example:

<sql id="sometable">
  ${prefix}Table
</sql>
<sql id="someinclude">
  from
    <include refid="${include_target}"/>
</sql>
<select id="select" resultType="map">
  select
    field1, field2, field3
  <include refid="someinclude">
    <property name="prefix" value="Some"/>
    <property name="include_target" value="sometable"/>
  </include>
</select>