Short Notes on SQL Basics

3 min readJun 23, 2022

SQL stands for Structured Query Language. This is designed to manage the data stored in relational databases. Relational database organizes the data in one or more tables with column and rows. The example is, data stored in excel sheets in the form of rows and columns. All data stored in relational database is a certain type of datatype such as integer, text (string), date and real (a decimal format).

Let’s see some of the basic commands of SQL and their usage.

CREATE
INSERT
SELECT
SELECT DISTINCT
COUNT
WHERE
WHERE with logical operators
BETWEEN
ORDER BY
GROUP BY
HAVING

CREATE

CREATE statement is used to create a table. The syntax is given below.

CREATE TABLE is a clause used to create a table. cricket_players is a name of table. There are 3 parameters are used, those are. name: TEXT, age: INTEGER , runs_scored: INTEGER .

INSERT

INSERT statement is used to add the records in the table. The syntax is shown below.

INSERT INTO is a clause used to insert the specific row and column into the table. Here Sachin is name variable, 48 is age variable and 15,000 are run_scored variable.

SELECT

SELECT statement is used to fetch data from database. The syntax is shown below.

SELECT clause selects the name column from cricket_players table. You can put some more column names beside name like shown below.

As you can see above SELECTclause selects two columns from cricket_players table those are name and age.

SELECT DISTINCT

Sometimes, it happens that, a column contains multiple repeated values or say duplicate values. It may happen that, two cricket players may have scored the same runs. If you want to select distinct values in the table then you can use SELECT DISTINCT clause. The syntax is shown below.

COUNT

If you want to count the number of players or the number of rows, then you can use, COUNT statement as shown below.

SELECT COUNT clause with asterisk mark in the bracket shows the number of records or number rows in the table.

Filtering the table

WHERE

WHERE statement allows you to filter text and numeric values in a table. The following operators can be used for conditional filtering.

= equal

<> not equal

< less than

> greater than

<= less than or equal to

>= greater than or equal to

Now let’s see an example,

As shown in the above code snippet, it filters out the particular movie i.e. Sholey from bollywood_films table.

WHERE with logical operators

You can combine queries with logical operators such as ANDor OR

Let’s see an example,

In the above example, all the films directed by David D and released after year 2010 were filtered out.

BETWEEN

BETWEEN statement provides shorthand for filtering values within specific range. This can be used in the following way.

With the combination of WHERE BETWEEN and AND we can filter out the films released between the year 2000 and 2010. Please note that, BETWEEN is inclusive.

Sorting and grouping the table

ORDER BY

This is a keyword in SQL used to sort the table either by ascending order or descending order. By default it sorts in ascending order.

In the above code snippet, the title column has been selected from bollywood_films table and ordered it in descending order by release_year .

GROUP BY

Sometimes you may need aggregate results, for example, you may want to count the number of films released each year by its count.

The above code snippet, the release_year column has been selected from the bollywood_films table and grouped by release_year and counts number of films in that year.

HAVING

The GROUP BY clause cannot be coupled withWHERE clause therefore to put the condition HAVING clause is being used.

The code snippet only shows those years in which 5 films were

In the next article let’s see joining data in SQL