QSpiders Full Stack Software Developer Interview Questions, Process, and Tips

Information technology

Q1. Structure query language
Ans. Used to perform tasks such as update data on a database, or retrieve data from a database.EXPLAIN works with SELECT , DELETE , INSERT , REPLACE , and UPDATE.
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Q2. What is a Primary Key?
Ans. 
A Primary Key is a unique identifier for each record in a database table.
• Uniquely identifies each record in a database table

• Must have a unique value for each record

• Cannot have NULL values

• Can be a single column or a combination of columns
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Q3. What is a Foreign Key?
Ans. 
A Foreign Key is a field in a database table that is used to establish a relationship with a primary key in another table.
• Used to enforce referential integrity between tables

• Helps maintain data consistency by ensuring that values in the foreign key column exist in the referenced table's primary key column

• Can be used to create one-to-many or many-to-many relationships between tables
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Q4. What is a Join? List its different types.?
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A Join is used to combine rows from two or more tables based on a related column between them.
• Types of Joins: Inner Join, Left Join, Right Join, Full Outer Join, Cross Join

• Inner Join: Returns rows when there is at least one match in both tables

• Left Join: Returns all rows from the left table and the matched rows from the right table

• Right Join: Returns all rows from the right table and the matched rows from the left tabl...read more
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Q5. What is the SELECT statement
Ans. 
The SELECT statement is used in SQL to retrieve data from a database.
• Used to specify which columns to retrieve from a table

• Can include conditions to filter the results using WHERE clause

• Can be used with functions like COUNT, SUM, AVG, etc.

• Example: SELECT column1, column2 FROM table_name WHERE condition;
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