![]() When we have used JSON_TABLE to convert our JSON document to a table, we can use the “SQL tool set” and perform relational operations like selection and aggregation on our data. The above query will return the following result: We also need to give the returned table a name, and here we call it people. The columns of the table to be returned with column name, type and the path within the JSON objects to where the value should be found.In this example, it is the objects of the people array. We can also use the ‘’ argument to get the whole JSON string. It is an optional argument, so we do not get any error. An empty array, empty object, or scalar value has depth 1. An error occurs if the argument is not a valid JSON document. then the upcoming MySQL 8 will do that for you. JSONDEPTH ( jsondoc) Returns the maximum depth of a JSON document. SELECT JSONOBJECT ( 'namefield', namefield, 'addressfield', addressfield, 'contactage', contactage ) FROM contact Aggregating JSON As a side note, if you do need to aggregate a resultset to json. SELECT id, productname, attributes FROM product This shows us the data in the JSON column, and it looks just like a text value. How do we do that We can run a simple SELECT statement to see the data in the table. We can retrieve the whole JSON document by removing the second argument. The functions in this section return attributes of JSON values. How to Read and Filter JSON Data in MySQL Once you’ve got some JSON data in a table, the next step is to read it. Path to the JSON array which should be converted into a table. SELECT JSONQUERY(data, '.employees 0') AS 'Result' It retrieves the first JSON object and gives you the following output.In other words, the JSON_TABLE function will be “called” once for each row of the preceding table.) Some visitors may just view the pages and other may view the pages and buy the products. MySQL JSON data type example Suppose, we have to track the visitors and their actions on our website. (Note that, as specified by the SQL standard, there is an implicit lateral join between the preceding table and the JSON_TABLE referring to this table. When you query data from the JSON column, the MySQL optimizer will look for compatible indexes on virtual columns that match JSON expressions. In this example, json_col refers to the column that contains our JSON document. The JSON data source: This expression may refer to columns of preceding tables in the FROM list. ![]() JSON_TABLE takes the following arguments: The path argument (if supplied) can include an optional path mode component. The path argument is optional (if you don’t provide it, the whole JSON document is returned). Since JSON_TABLE returns a result set, it may be used in the FROM clause. JSONQUERY ( expression, path ) Where expression is the JSON string expression, and path is the object or array that you want to extract from that expression.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |