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To better understand the semantics of conses and lists, a graphical representation of this kind of structures is often used. A cons cell is usually represented with two boxes in contact, that contain either two arrows that point to the car and cdr values, or directly the values. For instance, the re...

To consume a REST API with RestTemplate, create a Spring boot project with the Spring boot initialzr and make sure the Web dependency is added: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dep...

The qsort() standard library function is a good example of how one can use void pointers to make a single function operate on a large variety of different types. void qsort ( void *base, /* Array to be sorted */ size_t num, /...

JSON_VALUE function enables you to take a data from JSON text on the path specified as the second argument, and use this value in any part of the select query: select ProductID, Name, Color, Size, Price, JSON_VALUE(Data, '$.Type') as Type from Product where JSON_VALUE(Data, '$.Type') = 'part' ...

Once JSON values are extracted from JSON text, you can use them ina any part of the query. You can create some kind of report on JSON data with grouping aggregations, etc: select JSON_VALUE(Data, '$.Type') as type, AVG( cast(JSON_VALUE(Data, '$.ManufacturingCost') as float) ) as cost from...

JSON_MODIFY function can be used to update value on some path. You can use this function to modify original value of JSON cell in UPDATE statement: update Product set Data = JSON_MODIFY(Data, '$.Price', 24.99) where ProductID = 17; JSON_MODIFY function will update or create Price key (if it do...

JSON_MODIFY function can be used to append new value to some array inside JSON: update Product set Data = JSON_MODIFY(Data, 'append $.tags', "sales") where ProductID = 17; New value will be appended at the end of the array, or a new array with value ["sales"] will be create...

If you have a "child table" formatted as JSON collection and stored in-row as JSON column, you can unpack this collection, transform it to table and join it with parent row. Instead of the standard JOIN operator, you should use CROSS APPLY. In this example, product parts are formatted as ...

In this example, Tags array may contain various keywords like ["promo", "sales"], so we can open this array and filter values: select ProductID, Name, Color, Size, Price, Quantity from Product CROSS APPLY OPENJSON(Data, '$.Tags') where value = 'sales' OPENJSON will op...

Since JSON is stored textual column, you might want to ensure that it is properly formatted. You can add CHECK constraint on JSON column that checks is text properly formatted JSON: CREATE TABLE ProductCollection ( Id int identity primary key, Data nvarchar(max) CONSTRAINT [Data shoul...

Queries that filter or sort data by some value in JSON column usually use full table scan. SELECT * FROM ProductCollection WHERE JSON_VALUE(Data, '$.Color') = 'Black' To optimize these kind of queries, you can add non-persisted computed column that exposes JSON expression used in filter or sort...

If you can use memory-optimized tables, you can store JSON as text: CREATE TABLE ProductCollection ( Id int identity primary key nonclustered, Data nvarchar(max) ) WITH (MEMORY_OPTIMIZED=ON) Advantages of JSON in in-memory: JSON data is always in memory so there is no disk access Ther...

PL/SQL uses IN, OUT, IN OUT keywords to define what can happen to a passed parameter. IN specifies that the parameter is read only and the value cannot be changed by the procedure. OUT specifies the parameter is write only and a procedure can assign a value to it, but not reference the value. IN ...

OPENJSON function parses collection of JSON objects and returns values from JSON text as set of rows. declare @json nvarchar(4000) = N'[ {"Number":"SO43659","Date":"2011-05-31T00:00:00","Customer": "MSFT","Price":59.99,"Q...

OPENJSON function parses collection of JSON objects and returns values from JSON text as set of rows. If the values in input object are nested, additional mapping parameter can be specified in each column in WITH clause: declare @json nvarchar(4000) = N'[ {"data":{"num":&quot...

OPENJSON can extract fragments of JSON objects inside the JSON text. In the column definition that references JSON sub-object set the type nvarchar(max) and AS JSON option: declare @json nvarchar(4000) = N'[ {"Number":"SO43659","Date":"2011-05-31T00:00:00"...

JSON may have complex structure with inner arrays. In this example, we have array of orders with nested sub array of OrderItems. declare @json nvarchar(4000) = N'[ {"Number":"SO43659","Date":"2011-05-31T00:00:00", "Items":[{"Price"...

In this example every positioned element creates its own stacking context, because of their positioning and z-index values. The hierarchy of stacking contexts is organized as follows: Root DIV #1 DIV #2 DIV #3 DIV #4 DIV #5 DIV #6 It is important to note that DIV #4, DIV #5 and D...

Sometimes, a list should just not display any bullet points or numbers. In that case, remember to specify margin and padding. <ul> <li>first item</li> <li>second item</li> </ul> CSS ul { list-style-type: none; } li { margin: 0; pad...

Using the overflow property with a value different to visible will create a new block formatting context. This is useful for aligning a block element next to a floated element. CSS img { float:left; margin-right: 10px; } div { overflow:hidden; /* creates block formatting context...