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MySQL learning notes: JSON nested array query

2022-06-11 03:08:00 【Mountain Ghost ballad me】

Environmental Science

MySQL 5.7

Let's assume that the data

Simple JSON Don't talk about it , It's simple , Make it a little more complicated ：

[
    {
    
        "type":[
            {
    
                "code":"xmf",
                "name":" Little bee "
            }
        ],
        "cities":[
            {
    
                "code":"1",
                "name":" Shanghai "
            }
        ],
        "oType":[
            {
    
                "code":"order",
                "name":" list "
            }
        ],
        "p":[
            {
    
                "code":"110",
                "name":" Hurry up "
            }
        ]
    }
]

stay MySQL In the database , It looks like this ：

Insert picture description here
The picture above is just for illustration , Whole above JSON The corresponding field of the string in the database is detail.

On the Internet, many are first {......} object , Then nest the array , But my data is [......], namely ： First, an array , Then nest the objects , Then nest the array .

In this case , How to query ？

MySQL Nested array query method

Now I want to check ,JSON The city field in the string is Shanghai .
Correct SQL:

SELECT * 
from `template_yutao` 
where json_contains( `detail`, json_object('cities', json_array(json_object('name', ' Shanghai '))))

Ideas ：json_contains effect ： Whether to include sub documents . Let's construct a sub document , Then enter it to query .

I have tried to use the extraction method , Want to abbreviate the above SQL：

--  Want to extract first cities This floor , Query again 
--  unfortunately , stay json_contains It can't write  *  or  **
SELECT * from `alsc_cs_minos_template_biz` 
where json_contains( `detail`, json_object('name', ' Shanghai '), '$[*].cities')
--  Then it was rewritten as   The following can be successful , however $[0] The equals limit becomes the first of the array , It is not convenient to expand in the future .
--  Studied for half a day , There is no way to extract one layer ; But the above query is enough .
-- In fact, because json_contains It can't write  *  or  **, It has been shown that it can not be extracted , Only extraction can be specified explicitly .
SELECT * from `alsc_cs_minos_template_biz` 
where json_contains( `detail`, json_object('name', ' Shanghai '), '$[0].cities')

explain ：
It needs to be said here , above json Inquire about , and MongoDB be similar , But it didn't MongoDB Powerful ,MongoDB Words , Just check it out ：

SELECT * 
from `template_yutao` 
where detail.cities.name = ' Shanghai ' --  This is not standard MongoDB How to write it , Just want to express the general meaning .

-- MongoDB Standard writing 
db.template_yutao.find('$.detail.cities.name', ' Shanghai ');

Mybatis combination

Suppose we use Mybatis-Generator Generate Mapper The code in the file is ：criteria The form of class .

Mapper.xml Form like ：

<if test="_parameter != null">
  <where>
    <foreach collection="oredCriteria" item="criteria" separator="or">
      <if test="criteria.valid">
        <trim prefix="(" prefixOverrides="and" suffix=")">
          <foreach collection="criteria.criteria" item="criterion">
            <choose>
              <when test="criterion.noValue">
                and ${criterion.condition}
              </when>
              <when test="criterion.singleValue">
                and t.${criterion.condition} #{criterion.value}
              </when>
              <when test="criterion.betweenValue">
                and t.${criterion.condition} #{criterion.value} and #{criterion.secondValue}
              </when>
              <when test="criterion.listValue">
                and t.${criterion.condition}
                <foreach close=")" collection="criterion.value" item="listItem" open="(" separator=",">
                  #{listItem}
                </foreach>
              </when>
            </choose>
          </foreach>
        </trim>
      </if>
    </foreach>
  </where>
</if>
<if test="orderByClause != null">
  order by ${@[email protected](orderByClause)}
</if>
<if test="page">
  limit #{pageIndex},#{pageSize}
</if>

Related classes XXXParam class , It's like the following form ：

protected abstract static class AbstractGeneratedCriteria {
    
      protected List<Criterion> criteria;

      protected AbstractGeneratedCriteria() {
    
          super();
          criteria = new ArrayList<Criterion>();
      }

      public boolean isValid() {
    
          return criteria.size() > 0;
      }

      public List<Criterion> getAllCriteria() {
    
          return criteria;
      }

      public List<Criterion> getCriteria() {
    
          return criteria;
      }

      protected void addCriterion(String condition) {
    
          if (condition == null) {
    
              throw new RuntimeException("Value for condition cannot be null");
          }
          criteria.add(new Criterion(condition));
      }

      protected void addCriterion(String condition, Object value, String property) {
    
          if (value == null) {
    
              throw new RuntimeException("Value for " + property + " cannot be null");
          }
          criteria.add(new Criterion(condition, value));
      }

      protected void addCriterion(String condition, Object value1, Object value2, String property) {
    
          if (value1 == null || value2 == null) {
    
              throw new RuntimeException("Between values for " + property + " cannot be null");
          }
          criteria.add(new Criterion(condition, value1, value2));
      }

      public Criteria andIdIsNull() {
    
          addCriterion("id is null");
          return (Criteria) this;
      }

      public Criteria andIdIsNotNull() {
    
          addCriterion("id is not null");
          return (Criteria) this;
      }

Then at this time , How to write the code ？

My method is to add the following method to it ：

/** * * @param cityList * @return */
 public Criteria andCityCodeJson(List<String> cityList) {
    
     if (cityList == null || cityList.size() == 0) {
    
         throw new RuntimeException("Value for cityList cannot be null");
     }
     StringBuilder cityStr = new StringBuilder();
     int size = cityList.size();
     for (int i = 0; i < size; i++) {
    
         if (i == size - 1) {
    
             cityStr.append("json_object('code', '").append(cityList.get(i)).append("')");
         } else {
    
             cityStr.append("json_object('code', '").append(cityList.get(i)).append("')").append(",");
         }
     }
     addCriterion("json_contains(detail, json_object('city', json_array(" + cityStr +")))");
     return (Criteria) this;
 }

MySQL JSON Method statement

The following is a brief description , Concise and comprehensive , Please refer to the official website for details ：
12.18.3 Functions That Search JSON Values