MyBatis XML 配置 - 查询汽车信息
The given code is a MyBatis XML configuration for a SELECT statement that retrieves car information from the database. Here's a breakdown of the different elements used:
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'
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'select * from car c left join cartype t on c.tid=t.tid': This is the SQL query that selects all columns from the 'car' table and performs a left join with the 'cartype' table using the 'tid' column.
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'
': This element is used to specify conditional clauses in the SQL query. In this case, it is used to enclose the condition for the 'cname' parameter. -
'
': This element is used to conditionally include a SQL fragment. It checks if the 'cname' parameter is not null and not empty, and if true, it adds the condition 'and cname like concat('%',#{cname},'%')' to the SQL query. -
'
': This element defines the result mapping for the query results. The 'id' attribute is used to uniquely identify this result mapping. The 'type' attribute specifies the Java type of the mapped result object, and the 'autoMapping' attribute with a value of 'true' indicates that MyBatis should automatically map the columns to the corresponding properties of the result object. -
'
': This element is used to map the primary key column of the 'car' table to the 'cid' property of the result object. -
'
': This element is used to map a related object (in this case, the car type) to a property of the result object. The 'property' attribute specifies the property name, and the 'javaType' attribute specifies the Java type of the related object. The 'autoMapping' attribute with a value of 'true' indicates that MyBatis should automatically map the columns to the corresponding properties of the related object. -
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' (inside ' '): This element is used to map the primary key column of the 'cartype' table to the 'tid' property of the related object.
Overall, this configuration allows you to retrieve car information from the database, including the associated car type. The result will be automatically mapped to the corresponding Java objects based on the specified result mapping.
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