Whether you are an aspiring software developer, data analyst, or data engineer, learning SQL is a must. Solving problems in SQL assignments & SQL homework help and is a great place to start. But, to gain acute mastery, you need to practice routinely and try to solve some tricky problems.
If you wish to gain complete mastery, you must be at heart with all the different SQL commands and syntax rules. Start your journey towards SQL mastery with this write-up, compiling a list of the most important and commonly used SQL commands and some code snippets.
Basic & Crucial SQL Syntax
The SELECT statement is near ubiquitous in SQL queries. The command highlights or defines the data to be returned during a query. Php assignment help, SELECT statements are used in conjunction with the FROM clause, which identifies the portion of the database the query is concerned about.
The WHERE statement lays down certain conditions in a query and filters information accordingly. When used alongside the SELECT statement, it extracts information that satisfies the associated clause.
- * – The WILDCARD Character
‘*’ is considered a wildcard character in SQL. It selects all the columns in a targeted table/database in conjunction with the SELECT statement.
- ‘.’-The DOT Operator
The DOT notation is another special character in SQL. Referred to as the membership operator, it links a particular SQL identifier with another identifier of which the former is a component—dot operators project column or field identifier with a table, view, or synonym.
Simply put, the ‘.’ notation specifies the particular portion of a table or database from whence to select the query result.
The JOIN clause combines rows from different tables based on a related column.
Consider the following example.
There are two tables à ORDERS and CUSTOMERS.
OrderID CustomerID OrderDate
10308 1 2022-09-15
10309 37 2022-08-13
10310 77 2022- 05-03
CustomerID CustomerName Country
1 Raul Gonzales Mexico
37 Nick Papadoulos Greece
77 Arthur Higgins United Kingdom
Note that the CustomerID column in the ORDERS table acts as a foreign key and links to the CustomerID column in the CUSTOMERS table. Thus, any join between the rows of these two tables will be done based on this common column.
Suppose the query is to find the customer name & order date associated with an order id. Then, we have to use the JOIN command as the query requires information from both the ORDERS and CUSTOMERS table and the SQL code will go something like this à
SELECT Order.OrderID, Customers.CustomerName, Order.OrderDate
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID
The result will return order ids, customer names, and order dates, combining information from both tables using all matching customer id values.
JOINS can be of different types, namely,
- INNER JOIN= Returns all matching elements in the tables concerned
- LEFT OUTER JOIN= Returns all elements in the left table and ONLY those elements in the right table that match with the left table records
- RIGHT OUTER JOIN = Returns all records from the right table and only those left table records that correspond with the right table
- FULL OUTER JOIN= Returns all records from the left table and the right table
Well, that’s about it for this write-up. Hope it comes in handy for quick revisions of crucial and common SQL commands. Programming homework help If you need professional SQL homework help, look for a reliable computer science homework help service online.
All the best!
Summary: Some SQL commands are fundamental to any query and commonly used across multiple scenarios. This article offers a quick glimpse of all those essential commands.
Author-Bio: Alley John is a database engineer working with a cloud service provider in the UK. He also provides SQL homework help to students at MyAssignmenthelp.com, a leading academic service provider.