How do you write a good SQL query?

Question

Provide Correct Formatting for the Query. . Remove Correlated Subqueries if not required. . Limit the results obtained by the query. . Remove The DISTINCT Clause if not required. . Avoid Functions in Predicates. . Avoid OR, AND, NOT operators if possible. . Use WHERE clause instead of HAVING clause whenever possible.

How do you write a SQL query for beginners?

Learn to write basic SQL Queries1What is the T-SQL? ... 2What is a Relational Database? ... 3What is a Data Table? ... 4Our First Query: SELECT Statement. ... 5Filtering the Data: WHERE Clause. ... 6Sorting the Data: ORDER BY Statement. ... 7Eliminating the Duplicate Data: DISTINCT Clause. ... 8Quiz.

How do I create a SQL query with better performance?

How Can You Select Which Queries to Optimize?1Consistently Slow Queries. ... 2Occasionally Slow Queries. ... 3Queries With Red Flags. ... 4Queries That Majorly Contribute to Total Execution Time. ... 5Define Your Requirements. ... 6Reduce Table Size. ... 7Simplify Joins. ... 8Use SELECT Fields FROM Instead of SELECT * FROM.

What makes good SQL code?

The formatting of SQL code may not seem that important,but consistent formatting makes it easier for others to scan and understand your code. SQL statements have a structure, and having that structure be visually evident makes it much easier to locate and verify various parts of the statements.

What are the 5 basic SQL commands?

Some of The Most Important SQL CommandsSELECT - extracts data from a database.UPDATE - updates data in a database.DELETE - deletes data from a database.INSERT INTO - inserts new data into a database.CREATE DATABASE - creates a new database.ALTER DATABASE - modifies a database.CREATE TABLE - creates a new table.

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