Conditional Statements in SQL | If Statements in SQL

What are Conditional Statements in SQL?

SQL conditional statements execute movements or statements in keeping with conditional exams. If explicit standards are met, a conditional remark plays a specified motion or aggregate of movements. It’s a must to observe that whilst SQL conditional statements organize database connections and server actions, they don’t filter out information. They filter out data in keeping with one criterion and don’t impact database efficiency.

Commonplace SQL conditional statements come with the CASE remark, the IF remark, and the NULLIF remark. Each and every has its distinctive use case and syntax, which we will be able to discover intimately on this article.

The CASE Commentary

SQL’s CASE remark handles conditional expressions like IF-THEN-ELSE in different pc languages. If prerequisites are right kind, a case remark returns THEN and terminates. If no situation is met or FALSE, it examines the ELSE sentence and prevents.

Syntax

CASE WHEN condition_1 THEN result_1 WHEN condition_2 THEN result_2 WHEN condition_n THEN result_n… ELSE end result END

Instance

Point out whether or not a scholar handed or failed an issue in keeping with his marks, assuming he wanted 250 out of 500.

SELECT student_id, first_name, last_name, topic, marks,
CASE
WHEN marks > 250 THEN 'PASSED'
ELSE 'FAILED'
END AS end result
FROM scholars;

Output

The DECODE Serve as

SQL DECODE replaces conditional values in question effects. Oracle Database and different databases use it maximum. Knowledge transformation, CASE remark simplification, and conditional price substitute are not unusual makes use of.

Syntax

DECODE(expression, search1, result1, search2, result2, …, default_result)

Instance 

If the “scholars” desk has this knowledge:

If the "scholars" desk has this knowledge:
| student_id | rating |
|------------|-------|
| 1          | 96    |
| 2          | 78    |
| 3          | 81    |
| 4          | 62    |
| 5          | 43    |

SELECT student_id, rating,
       DECODE(
         WHEN rating >= 90 THEN 'A'
         WHEN rating >= 80 THEN 'B'
         WHEN rating >= 70 THEN 'C'
         WHEN rating >= 60 THEN 'D'
         ELSE 'F'
       ) AS grade
FROM scholars;

Output

This end result provides letter grades in keeping with scholar rankings the usage of DECODE.

COALESCE

COALESCE() is a legitimate SQL serve as that returns the primary non-NULL parameter price. It’s in most cases used for database NULL dealing with. As a substitute of changing NULL values on the utility stage, it handles them upon information retrieval.

Syntax

COALESCE(value_1, value_2, …., value_n)

Instance

Take a look at underneath the enter desk ‘customer_contact’:

ID
Phone_number
1
2
+9 312-985-7824
3
+9 187-765-4329

SELECT ID, COALESCE(Phone_number, 'NULL') AS Phone_Number
FROM customer_contact;

Output

This situation makes use of COALESCE() to interchange NULL entries within the Phone_Numbers column with ‘NULL’ for consistency.

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GREATEST

You’ll be able to use the SQL GREATEST serve as to search out the biggest price in a suite of values. GREATEST() accepts n parameters. 

Syntax

GREATEST ( expr1, [expr_n] )

Instance

SELECT
GREATEST(6, 15, 25, 43, 69) AS GREATEST_CHECK,

Output

IFNULL

The SQL IFNULL serve as is very important for builders and analysts searching for to grasp database control. Its core serve as—seamlessly changing NULL values with an outlined choice—allows information integrity and research.

Syntax  

IFNULL is constructed on simplicity and potency. This method cleanly replaces NULL values with a given substitute.

IFNULL(expression, replacement_value)

Instance 

When the parameter is an empty set, SUM, AVG, MAX, and MIN combination purposes go back null. On this instance, the IFNULL serve as returns a price as a substitute of a null when the serve as evaluates to an empty set:

IFNULL(SUM(worker.wage)/25, -1)

Output

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IN

The SQL IN situation (or IN operator) means that you can temporarily test if an expression suits any access in a listing. It reduces the collection of OR prerequisites in SELECT, INSERT, UPDATE, and DELETE statements.

Syntax 

The SQL IN situation syntax is:

expression IN (value1, value2, …. value_n);

or

expression IN (subquery);

Instance 

The IN situation works with all SQL information varieties. Take a look at it with personality (string) values. A desk known as providers comprises the next information:

SELECT *
FROM providers
WHERE supplier_name IN ('EY', 'Oracle', 'Microsoft');

Output

Make a selection 3 data. Those are the predicted effects:

LEAST

Not like GREATEST, SQL LEAST returns the “least” or smallest price in a suite of values.

Syntax

LEAST ( expr1, [expr_n] )

Instance

SELECT
LEAST('10', '15', '65', 8') AS LEAST_CHECK;

Output

NULLIF

NULLIF takes two arguments, expr1 and expr2. If expr1 and expr2 are equivalent, NULLIF returns NULL; in a different way, it returns expr1. The primary parameter cannot be NULL, in contrast to the opposite null dealing with process.

Syntax

SELECT NULLIF (expression1, expression2);

Instance

This situation yields NULL because the first and 2nd arguments fit:

SELECT 
    NULLIF(10, 10) end result;

Output

For the reason that two arguments don’t seem to be equivalent, the next instance yields the primary:

SELECT 
    NULLIF(20, 10) end result;

Output

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Dealing with NULL Values with Conditional Statements

Rows with out column values have null values. Null values are unknown, now not 0 or blanks. Null values can be utilized in WHERE and HAVING clauses. Null values can’t be much less, equivalent, or more than the situation price.

As mentioned, SQL Server has NULL price dealing with purposes.

• The ISNULL() serve as makes use of two parameters to interchange NULL values with a given price.
• COALESCE(): In a vast listing, it returns the primary non-null expression.

Sensible Programs of Conditional Statements in SQL

Listed below are a couple of very important packages of conditional statements.

1. Stock Keep watch over Control Database

• Any product-based trade will have to observe its stock. Knowledge analysts make the most of SQL to construct a list control gadget to lend a hand trade house owners make very important stock making plans selections.
• As an example, take a Walmart store gross sales dataset (12 months, Month, Product Class, Gross sales) for a given length. Come with GDP, CPI, cotton manufacturing, unemployment, and many others. You’ll be able to get climate and vacation information. Use the dataset to increase an SQL on-line retail utility database for information research on this SQL challenge.

2. Eu Football Sport Research

• This SQL challenge is very best for you for those who love football and revel in taking a look at tendencies in several groups. It is going to educate you combination the dataset the usage of the question language.
• Use the dataset to create a SQL database. Use SQL’s Conditional SELECT command to view desk values. Mix tables the usage of specified JOIN instructions in keeping with values. Analyze staff and participant information the usage of ORDER BY, GROUP BY, and LIMIT. Additionally, rank groups the usage of combination purposes.

3. Blood Financial institution Control Gadget

• Blood banks retailer and distribute blood. The Blood Financial institution Control Gadget is helping all blood banks observe blood high quality and availability when sufferers request it. If you need healthcare SQL observe initiatives, do that one.
• A blood donation database will have to come with information about donors (title, age, blood workforce), recipients, hospitals that want blood from the blood financial institution, blood high quality (inflamed or now not), and many others.

4. Bookshop Research/ Library Control Gadget 

• Suppose again to college. You will have to have observed many books. Create a digital book place together with your favourite books.
• Imagine working a book place chain. To create a pattern dataset of your favourite books, come with Book_ID, Title, Publishing Title, ISBN, Version, No. of pages, Gross sales, Town, and Value in a desk.

Conclusion

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FAQs

1. How does the IF remark fluctuate from the CASE remark in SQL?

The IF remark in SQL is ceaselessly used to conditionally execute chunks of procedural code, equivalent to saved procedures, purposes, and triggers. CASE queries go back values in keeping with SELECT, WHERE, and ORDER BY clauses.

2. What are IFNULL, NULLIF, and COALESCE used for in SQL?

• If now not NULL, IFNULL returns the primary argument. Returns the second one argument if NULL.
• NULLIF returns null if each arguments are similar. SQL makes use of this serve as to check two values.
• COALESCE returns the primary non-null parameter. Returns null if all parameters are null.

3. How are you able to use conditional statements with purposes to create complicated queries?

Along with AND, OR, and NOT, you’ll be able to create sophisticated SQL prerequisites by way of blending SQL conditional statements. Subqueries, EXISTS, ANY, ALL operators, or nesting CASE expressions can do that.

4. Are conditional statements in SQL case-sensitive?

SQL is in most cases case-insensitive. Alternatively you write your SQL key phrases, the database engine will learn them as it should be, yielding the similar end result irrespective of the key phrase case.

5. Can I take advantage of conditional statements with combination purposes in SQL?

We will upload a suite of prerequisites to the present Combination purposes. Some common combination purposes are: 

• Depend the collection of rows that satisfy the prerequisites the usage of COUNT(). 
• The SUM() serve as returns the overall sum of a numeric column.
• Max() and MIN() yield the biggest and smallest values that satisfy question prerequisites.
• AVG() calculates the typical of outlined values.
• GROUP BY summarizes rows with similar values. Used with combination purposes like COUNT, SUM, and many others.