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1) What is SQL and its significance in software testing? SQL (Structured Query Language) is a programming language used to manage and manipulate relational databases. 2) What are the different types of SQL statements? SQL statements can be classified into four main types: Data Manipulation Language (DML): Used to manipulate data in the database (e.g., SELECT, INSERT, UPDATE, DELETE). Data Definition Language (DDL): Used to define and modify database structures (e.g., CREATE, ALTER, DROP). Data Control Language (DCL): Used to control access and permissions on the database (e.g., GRANT, REVOKE). Transaction Control Language (TCL): Used to manage transactions in the database (e.g., COMMIT, ROLLBACK). Data Query Language (DQL) is a subset of SQL (Structured Query Language) used to retrieve data from a database (e.g., SELECT). Constraints in SQL Constraints are the conditions or rules applied to the data in a table. They are used to set limitations on the type of data that can be entered or manipulated within a table, ensuring data integrity, accuracy, and consistency. Different Types of Constraints in SQL: NOT NULL Constraint: Enforces a column to NOT accept NULL values. UNIQUE Constraint: Ensures that all the values in a column are unique. PRIMARY KEY Constraint: Uniquely identifies each row in a table. Combines the functionality of NOT NULL and UNIQUE. FOREIGN KEY Constraint: A foreign key is a field in a table that refers to the primary key of another table. It establishes a relationship between two tables by linking a column in one table to the primary key of another. CHECK Constraint: Ensures that all the values in a column satisfy a specific condition. DEFAULT Constraint: Assigns a default value to a column if no value is provided. Joins in SQL Joins in SQL are used to combine rows from two or more tables based on a related column between them. INNER JOIN: Returns rows when there is a match in both tables. LEFT JOIN: Returns all rows from the left table and the matching rows from the right table. If there is no match, NULL values are returned for the right table's columns. RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and the matching rows from the left table. If there is no match, NULL values are returned for the left table's columns. FULL JOIN (or FULL OUTER JOIN): Returns rows when there is a match in either the left or right table. If there is no match, NULL values are returned for the columns of the table without a match. Self-join: A self-join is a join operation where a table is joined with itself. DROP vs TRUNCATE DROP: Deletes the entire table (or other database objects such as views, indexes, etc.) from the database, including its structure and data. TRUNCATE: Deletes all rows from a table, but the table structure (schema) remains intact. It only removes the data. DELETE vs TRUNCATE DELETE: Used to delete specific rows from a table based on a condition. Can include a WHERE clause to specify which rows to delete. TRUNCATE: Used to remove all rows from a table, keeping its structure intact. Does not allow a WHERE clause; all rows are removed. Clauses in SQL INSERT: Adds new rows to a table. UPDATE: Modifies existing rows in a table. DELETE: Removes rows from a table. SELECT: Used to select data from a database. FROM: Identifies the source table or tables in a database. WHERE: Used to filter records based on a condition. Like The LIKE operator is used in a WHERE clause to search for a specified pattern in a column. ORDER BY Clause Sorts the result based on one or more columns, either in ascending (ASC) or descending order. GROUP BY Clause Groups rows of data with the same values in specified columns in a SELECT statement, often used with aggregate functions like COUNT, SUM, AVG, etc. HAVING Filters groups after grouping with GROUP BY. IF Clause The IF clause in SQL is used for conditional logic in procedural code to execute statements based on whether a condition is true or false. Stored Procedure A Stored Procedure in SQL is a precompiled set of one or more SQL statements that are stored on the database server and can be executed as a single unit. It allows for reusable and modular SQL code execution. The Difference Between Primary Key and Unique Key Primary Key: A table can have only one primary key. It does not allow NULL values. It uniquely identifies each row in a table. Unique Key: A table can have multiple unique keys. It allows NULL values (but only one NULL value is allowed in a column). It ensures that all values in the column are unique, but doesn't necessarily identify rows like a primary key does. The Difference Between Primary Key and Foreign Key Primary Key: A primary key uniquely identifies each row in a table. It cannot have NULL values. Each table can have only one primary key. It is used to establish the uniqueness of a record in the table. Foreign Key: A foreign key is a column (or a set of columns) that links one table to another. It refers to the Primary Key in another table. It can have NULL values. A table can have multiple foreign keys. It is used to maintain referential integrity between two tables. You said: what are the different function sof sql ChatGPT said: ChatGPT Different Functions of SQL SQL provides a variety of functions to perform operations on data stored in a database. These functions can be broadly classified into the following categories: 1) Aggregate Functions Aggregate functions operate on a set of values and return a single value, often used with the GROUP BY clause. COUNT(): Returns the number of rows. Example: SELECT COUNT(*) FROM employees; SUM(): Returns the total sum of a numeric column. Example: SELECT SUM(salary) FROM employees; AVG(): Returns the average value of a numeric column. Example: SELECT AVG(salary) FROM employees; MIN(): Returns the smallest value in a column. Example: SELECT MIN(salary) FROM employees; MAX(): Returns the largest value in a column. Example: SELECT MAX(salary) FROM employees; 2) String Functions String functions are used to manipulate and analyze string data. UPPER(): Converts a string to uppercase. Example: SELECT UPPER(name) FROM employees; LOWER(): Converts a string to lowercase. Example: SELECT LOWER(name) FROM employees; LENGTH(): Returns the length of a string. Example: SELECT LENGTH(name) FROM employees; SUBSTRING(): Extracts a portion of a string. Example: SELECT SUBSTRING(name, 1, 3) FROM employees; TRIM(): Removes leading or trailing spaces from a string. Example: SELECT TRIM(name) FROM employees; CONCAT(): Combines two or more strings. Example: SELECT CONCAT(first_name, ' ', last_name) FROM employees; 3) Date and Time Functions Date and time functions are used to manipulate date and time data. NOW(): Returns the current date and time. Example: SELECT NOW(); CURDATE(): Returns the current date. Example: SELECT CURDATE(); CURTIME(): Returns the current time. Example: SELECT CURTIME(); DATE(): Extracts the date portion from a datetime.