The method to distinguish the presence of a JSON field in an array using Presto is to use the "json_extract" function. This function can extract the value of a JSON field from a given JSON object or array.
To determine the presence of a JSON field in an array, you can use the "jsonextractscalar" function with the "cardinality" function. The "jsonextractscalar" function is used to extract the scalar value of a JSON field, and the "cardinality" function is used to determine the number of elements in the result set. If the result set has a cardinality greater than zero, it means that the JSON field is present in the array.
For example, to determine if a JSON field called "color" is present in an array called "my_array", you can use the following query:
SELECT cardinality(jsonextractscalar(myarray, '$[*].color')) > 0 AS iscolorpresent FROM mytable
In this query, the "jsonextractscalar" function is used to extract the value of the "color" field from all elements in the "my_array" array. The "cardinality" function is used to determine the number of elements in the result set, which indicates the presence or absence of the "color" field in the array. The result set of this query will be a boolean value indicating whether the "color" field is present in the array.
Please start posting anonymously - your entry will be published after you log in or create a new account. This space is reserved only for answers. If you would like to engage in a discussion, please instead post a comment under the question or an answer that you would like to discuss
Asked: 2021-12-12 11:00:00 +0000
Seen: 13 times
Last updated: May 06 '21
In SCSS, what is the method for grouping and reusing a set of classes and styles?
What is Nextflow for genomics in AWS?
What does "waiting for handler commit" mean in relation to the slow writes experienced in MySQL 8?
What is the best way to arrange the file structure for both the backend and frontend in MERN?
What are the differences between EJS/Handlebars and Nextjs?
How can a Python function (REFPROP 9.1) be turned into a vectorized version?