How to use the if-else tag in MyBatis?

2 years ago
Jackson Davis
1 minute

In MyBatis, you can use the tag to implement conditional judgment, similar to the if-else statement in a program. Here is an example:

<select id="selectUsers" parameterType="map" resultType="User">
  SELECT * FROM users
  <where>
    <if test="username != null">
      AND username = #{username}
    </if>
    <if test="email != null">
      AND email = #{email}
    </if>
  </where>
</select>

In the example above, SQL statements are dynamically concatenated based on the incoming parameters. If the username or email is not empty, the corresponding conditions will be added. The test attribute in the tag is used to specify the expression for condition judgment, and the corresponding content will only be executed when the value of the expression is true.

It is important to note that when using multiple tags to implement multiple condition judgments, attention should be paid to the logical relationships between the conditions, such as using AND or OR to connect them. If the conditions are complex, and tags can be used to implement more sophisticated condition judgment logic.

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