Mastering SQL: A Comprehensive Guide to SQL Commands

The relational database management and manipulation language SQL (Structured Query Language) is employed. Data in a database can be created, retrieved, updated, and deleted using this method. MySQL, Oracle, and Microsoft SQL Server are just a few of the database management systems that use the standard language SQL.

By specifying the arrangement of tables, columns, and data types, SQL is used to build and administer databases. Additionally, it may be used to make changes to and remove database objects including tables, indexes, and views. Using SELECT queries, SQL may be used to insert, update, and delete data from databases as well as retrieve data from them.

By creating and managing users and roles, issuing and revoking rights, and controlling access to data, SQL also offers a mechanism to manage database security. Additionally, it offers a means of backing up databases, restoring them when necessary, and performing data recovery.

Many different businesses, including finance, healthcare, retail, and many others, use SQL extensively. Anyone dealing with databases must have a solid grasp of SQL since it is a potent tool for managing and manipulating data in large, complicated databases.

Basic SQL Commands are:

SELECT => Select data from the database
FROM => Specify the table we ‘re pulling from
WHERE => Filter Query to match the condition
AS => Rename column or table with an alias
JOIN => Combine rows from 2 or more tables
AND =>Combine Query Conditions.
OR => Combine Query Conditions.
LIMIT => Limit rows returned.
IN => Specify Multiple values when using WHERE
CASE => Return a value on a specific condition
IS NULL => Return only rows with a null value
LIKE => Search for patterns in the column
COMMIT => Write transaction to the database
ROLLBACK => Undo the Transaction block
ALTER TABLE => Add or Remove columns from the table
UPDATE => Update table data
DELETE =>Delete rows from a table
CREATE =>Create Table, Database, or Index
INSERT => Add a single row to the table
DROP => DELETE Table, Database, or Index
GROUP BY => Group data into logical sets
ORDER BY => Set the order of the result
HAVING => Same as WHERE but filters group
COUNT =>Count the number of rows
SUM => Return the sum of the column
AVG => Return average of the column
MIN => Return min value of the column
MAX => Return max value of the column

1) SELECT => Select data from the database

A SELECT query produces a table with the supplied columns and rows that fulfill the conditions. A basic SELECT statement has the following syntax:

SELECT FROM table name,
SELECT column1, column2,… WHERE situation;

In a SELECT query, you can change the data before it is returned by using various functions, aggregate functions, and join procedures. The SELECT statement is one of the most popular SQL procedures and serves as the foundation for numerous database processes.

2) FROM => Specify the table we’re pulling from

A SQL SELECT statement’s FROM clause specifies the table(s) from which data is to be fetched. The FROM clause has the following fundamental syntax:

SELECT table name FROM

You can also use a join operation to retrieve data from many tables by supplying multiple table names separated by a comma. The join procedure joins rows from two or more tables based on a shared column.

3) WHERE => Filter Query to match the condition

In a SQL SELECT statement, the WHERE clause is used to filter data based on certain conditions. It specifies a condition that must be met for a row to be included in the result set. A WHERE clause’s basic syntax is as follows:

WHERE is the condition

The condition can be a comparison operator (e.g., =, >) or a set of conditions linked together by logical operators (e.g. AND, OR).

4) AS => Rename column or table with an alias

The AS clause in SQL is used to give a column or table a temporary name, known as an alias. An alias can make it easier to reference a column or table in a query, especially when the original name is long or complex. The syntax for assigning an alias to a column is:

SELECT column_name AS alias_name
FROM table_name;

And the syntax for assigning an alias to a table is:

SELECT column_name
FROM table_name AS alias_name;

The alias only exists for the duration of the query and does not affect the actual name of the column or table in the database.

5) JOIN => Combine rows from 2 or more tables

In SQL, the JOIN clause is used to join rows from two or more tables based on a common column between them. A join produces a new table that contains columns from both tables and only rows where the join condition is met. There are various sorts of joins, such as inner join, left join, right join, and full outer join, each of which returns a distinct subset of the data depending on the join condition.

A join has the following fundamental syntax:

FROM table1 JOIN table2 ON table1.column = table2.column;

The ON clause sets the join condition, which determines which rows are combined. The SELECT command indicates which columns in the result set should be returned. It is possible to join tables.

6) AND => Combine Query Conditions.

The AND operator in SQL is used to combine two or more conditions in a WHERE clause, where all conditions must be met for a row to be included in the result set. The AND operator is a logical operator that returns a result of TRUE only if all its operands are TRUE. The syntax for using AND in a WHERE clause is:

WHERE condition1 AND condition2 AND …;

7) OR => Combine Query Conditions.

OR is a logical operator that combines two or more conditions and returns true if at least one of them is met. It denotes “either/or”.

For example, if you want to obtain records where the client is from either California or New York, you might use the OR operator in a database query. The query returns entries where the consumer is from either California or New York.

8) LIMIT => Limit rows returned.

LIMIT is a SQL (Structured Query Language) clause that specifies the maximum number of rows that will be returned from a query. It limits the results to a certain number of rows. For example, in a query to return the top ten customers with the highest sales, the LIMIT clause would be used to limit the results to only 10 rows.

Similar clauses, such as FETCH and TOP, can be used to limit the number of rows returned in other database management systems.

9) IN => Specify Multiple values when using WHERE

IN is a SQL operator that specifies multiple values to be searched for in a single column in the WHERE clause. It checks to see if a value is in a list of values.

To obtain all customers who purchased the states of California, New York, or Texas, for example, use the IN operator in the WHERE clause with the values ‘California,’ ‘New York,’ and ‘Texas’. The query would return all rows with one of the provided values in the state field.

10) CASE => Return a value on a specific condition

CASE is a conditional statement in SQL used to return a value based on a specific condition. It acts as a substitute for the IF-THEN-ELSE statement. The CASE statement evaluates a list of conditions and returns a result when a matching condition is found.

For example, in a query to classify customers as “Gold”, “Silver” or “Bronze” based on their total sales, you would use the CASE statement to evaluate each customer’s sales and return the appropriate classification. The result would be a column in the query output that shows the customer’s classification.

11) IS NULL => Return only rows with a null value

IS NULL is a SQL operator that returns only rows with a null (undefined or unassigned) value in a specified column in the WHERE clause. A null value in a database denotes the lack of data and is not the same as an empty string or zero.

The IS NULL operator checks a column for the presence of a null value and returns true if it exists. In a query to obtain all clients who have not yet submitted their phone numbers, for example, the IS NULL operator in the WHERE clause would be used to test for the presence of null values in the phone number field. The query would return all rows with a null phone number column.

12) LIKE => Search for patterns in the column

LIKE is a SQL operator that is used in the WHERE clause to find specific patterns in a column. It allows you to compare a string value to a pattern that contains wildcard characters. The wildcard characters % and _, respectively, can represent any number of characters and a single character.

For example, in a query to obtain all customers whose names start with “Jo”, you would use the LIKE operator in the WHERE clause with the pattern ‘Jo%’ to match any name that starts with “Jo”.

The query would return all rows with names beginning with “Jo” in the name field. When looking for values in a column, the LIKE operator is handy for searching for approximate matches and ignoring case sensitivity.

13) COMMIT => Write transaction to the database

COMMIT is a SQL command that saves database changes made during a transaction. A transaction is a collection of database actions performed as a single unit of work. The COMMIT command indicates the conclusion of a transaction and permanently stores all changes made during the transaction in the database.

Changes are only visible to the user who made them until a transaction is committed; they are not available to other users or apps accessing the database. If an error occurs during a transaction, the ROLLBACK command can be used to roll back the transaction, which undoes all changes performed during the transaction. The COMMIT command is used to assure database data integrity and consistency.

14) ROLLBACK => Undo the Transaction block

ROLLBACK is a SQL command that undoes all changes made during a transaction. It undoes the consequences of a transaction and restores the database to its pre-transaction state. When a transaction cannot be completed successfully, the ROLLBACK command is used to undo all changes made during the transaction.

If an error happens during a transaction that modifies several records, for example, the ROLLBACK command can be used to undo the changes made to all records, ensuring that the database remains consistent. To ensure data integrity and consistency in a database, the ROLLBACK command is often used in conjunction with the COMMIT statement.

15) ALTER TABLE => Add or Remove columns from the table

The ALTER TABLE statement lets you add or remove columns from a database table. It is used to change the structure of a table by adding new columns, removing existing columns, and changing column data types. This statement is a valuable tool for managing database tables, but it must be used with caution to avoid data loss.

16) UPDATE => Update table data

The UPDATE statement modifies existing data in a table. By setting a criterion for which records to update, you can edit individual fields or all fields in one or more entries in a table. It’s a useful tool for keeping and updating data in a database.

17) DELETE => Delete rows from a table

The DELETE statement is used to delete rows from a database table. You can set a criterion to decide which rows to delete, providing you control over what data is erased. It is a necessary tool for managing data in a database, but it must be used with caution because erased data cannot be retrieved.

18) CREATE => Create Table, Database, or Index

The CREATE statement is used to create new objects in a database, including tables, databases, and indexes. It allows you to define the structure and attributes of these objects, such as the names and data types of columns in a table or the type of index to be created. This statement is essential for setting up and organizing data in a database.

19) INSERT => Add a single row to the table

The INSERT statement is used to insert new data into a database table. It lets you insert a single row or several rows into a table at the same time. The values to be entered must correspond to the number and type of columns in the table. The INSERT statement is useful for populating and expanding data in a database.

20) ROP => DELETE Table, Database, or Index

The DROP statement is used to delete objects in a database, including tables, databases, and indexes. It permanently removes the object and all associated data and should be used with caution as dropped data cannot be recovered. The DROP statement is an important tool for managing objects in a database, but it should be used carefully to avoid accidental data loss.

22) ORDER BY => Set the order of the result

The SQL ORDER BY clause is used to arrange the query result set in ascending or descending order depending on one or more columns. The ORDER BY clause defines which columns will be sorted, and the optional DESC keyword will sort the data in descending order.

The ORDER BY clause organizes the data in ascending order by default. The ORDER BY clause is a useful tool for presenting facts in a sensible and orderly fashion.

23) HAVING => Same as WHERE but filters group

The SQL HAVING clause is similar to the WHERE clause in that it filters groups of rows in a result set. Following the GROUP BY clause, the HAVING clause filters groups of rows based on aggregate functions like SUM, AVG, or COUNT. The HAVING clause allows you to apply conditions to groupings of data in a table, making it a useful tool for sophisticated data analysis and summarization.

24) COUNT => Count the number of rows

In SQL, the COUNT function counts the number of rows in a result set. The COUNT function returns the number of rows that satisfy a given criterion, or all rows if no condition is specified. The COUNT function is useful for examining the size and structure of data in a table, and it is frequently combined with other aggregate functions, such as SUM or AVG, to do more comprehensive data analysis.

25) SUM => Return the sum of the column

The SQL SUM function returns the total sum of data in a specified column. The SUM function takes as an argument a column name and returns the total sum of all the values in that column. It’s useful for performing mathematical calculations and data analysis on massive datasets.

To perform more extensive data analysis, the SUM function is frequently used in conjunction with other aggregate functions such as COUNT or AVG.

26) AVG => Return average of the column

The AVG function in SQL is used to calculate the average value of a column in a result set. It takes a column name as its argument and returns the average of all the values in that column. The AVG function is an important tool for performing mathematical calculations and data analysis and is commonly used in combination with other aggregate functions, such as COUNT or SUM, to perform more complex data analysis.

The AVG function can provide insights into the central tendency and distribution of data in a column.

27) MIN => Return min value of the column

In SQL, the MIN function returns the lowest value in a given column. It accepts a column name as an argument and returns the value with the least value in that column. The MIN function is useful for determining the minimum or lowest value in a column, and it is frequently combined with other aggregate functions such as MAX or AVG to accomplish more complex data analysis.

28) MAX => Return max value of the column

In SQL, the MAX function returns the maximum value in a specified column. It accepts as an argument a column name and returns the biggest value in that column. The MAX function is useful for determining the maximum or greatest value in a column, and it is frequently combined with other aggregate functions such as MIN or AVG to accomplish more complex data analysis.

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Mastering SQL: A Comprehensive Guide to SQL Commands

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