Reading Syntax Diagram in SQL

In this tutorial we will look at the method we require to read and understand a Syntax Diagram in SQL.

What are Syntax Diagrams in SQL?

When we write any logical implementation there is a thought process that works behind the hood. The diagrammatic representation of any complex logic makes it easy to understand for all despite the level of knowledge one has.

In SQL, the syntax diagrams are made to understand and manifest the underlying logic.

Syntax diagrams lie in the core when we need to document the building blocks of any application with a working backend system. It is made up of various data entries and plenty of illustrations consisting of different types of connectors and containers.

We have almost all possible combinations possible, which makes it an important method of documentation.

Let us now try to read about some of the prominent illustrations which are put to use in the syntax diagrams.

How to read and understand SQL Syntax Diagrams?

Some of the most important diagrammatic representations put to use while we make a Syntax diagram are as follows:

1. When we have two right arrowheads and a line [►►──] this signifies the starting of a syntax diagram.

2. When a line and a single right arrowhead [ ──►] are present it means that the syntax is moving forward in the next line.

3. When we have a right arrowhead and a line[ ►── ]indicates that the syntax is in continuation from the previous line.

4. When a line is present with a right arrowhead and a left arrowhead [──►◄] this indicates the completion of any syntax diagram.

5. The syntax fragments start with a vertical bar and hyphens[ |── ] and end with hyphens and a vertical bar[ ──| ].

6. Items that are mandatory for the query to work appear on the main horizontal path, while the optional ones appear below the main path.

7. When an optional item is present above the main path, it signifies that it has no contribution to the execution of the query. Such variables are put up to make the query more readable. Example: Alias of columns or tables.

8. When we need to select between two or more items they always appear as a stack one on the other.

9. If the stack appears on the main path, it means at least one choice needs to be made to execute the query.

10. If the stack appears below the main path then the selection remains optional.

11. If one choice is in selection by default it appears above the main path and rest all appear below the main path.

12. All the keywords appear in capitals and the spelling should be correct as well. Example: INSERT, UPDATE, DELETE, etc.

13. All the user-specified variables should be written in lowercase letters. Example: user-variable. They are the variables that will be sent by the user into the query.

14. If the syntax diagram has some punctuation marks or other symbols, then they need to be included in the syntax of the query for error-free execution of the query for the transaction on the database.

15. Functions or code blocks should be defined and then put on the main path to ensure error-free execution of our query.

16. The adjacent segments which occur between large bullets (●) can be specified in any sequence given by the user.

Summary

In this tutorial, we saw all about SQL Syntax Diagrams.

We started with the definition and the need for using a Syntax Diagram. From there we saw and understood various methods of diagrammatic representations to present different properties of a query.

We need to be careful while creating a Syntax diagram. The main path is the major flow system of the query and all the other parameters are present on, above or below the main path. The location depends on the priority of each parameter.

With the syntax diagram, we can easily document our application logic.