There is no index in the database table. When inserting data, SQL statements are used to prevent repeated addition (Reprint)

INSERT IGNORE INTO table(aaa,bbb)
SELECT '1111','2222' FROM DUAL
WHERE NOT EXISTS(
  SELECT id FROM table WHERE bbb= '2222'
)

mybaits

<insert id="addItemCharacteristic" parameterType="com.orderalliance.entity.CharacteristicDTO">
        <!--INSERT INTO table (item_id,characteristic) VALUES(#{aaa,jdbcType=BIGINT},#{bbb,jdbcType=VARCHAR})-->
        <!-- this sql Statement to prevent repeated addition of data -->
        INSERT IGNORE INTO table (aaa,bbb)
        SELECT #{111,jdbcType=BIGINT},#{222,jdbcType=VARCHAR} FROM DUAL
        WHERE NOT EXISTS(
            SELECT id FROM table WHERE bbb= #{bbb,jdbcType=VARCHAR}
        )
</insert>

 Key code 

INSERT IGNORE INTO  Table name (' Field ') 
 SELECT ' Data when the field needs to be inserted ' FROM dual 
WHERE NOT EXISTS
 (SELECT * FROM ' Table name ' WHERE ' Fields that need to be restricted from repetition ' = ' Restricted field the data inserted this time ')


 key word 

IGNORE

NOT EXISTS