SQL Basics: DDL, DML, Querying and Functions

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Questions and Answers

Which type of SQL command is primarily used for modifying the structure of a database, such as adding or removing columns from a table?

  • Data Control Language (DCL)
  • Transaction Control Language (TCL)
  • Data Definition Language (DDL) (correct)
  • Data Manipulation Language (DML)

In SQL, which command is used to remove rows from a table?

  • DROP
  • ERASE
  • REMOVE
  • DELETE (correct)

When retrieving data from a table, which SQL clause is used to filter the results based on a specific condition?

  • FILTER
  • HAVING
  • ORDER BY
  • WHERE (correct)

Which type of join returns all rows from the left table and the matching rows from the right table, padding with NULLs if there is no match?

<p>Left Outer Join (D)</p> Signup and view all the answers

What is the primary purpose of using DISTINCT in a SELECT statement?

<p>To eliminate duplicate rows from the result set (D)</p> Signup and view all the answers

Which SQL command is used to add new data into a table?

<p>INSERT (D)</p> Signup and view all the answers

What does the SQL command ALTER TABLE do?

<p>It modifies the structure of an existing table. (C)</p> Signup and view all the answers

Which of the following is an aggregate function in SQL?

<p>AVG (C)</p> Signup and view all the answers

What is the purpose of a PRIMARY KEY constraint in a database table?

<p>To uniquely identify each record in the table. (B)</p> Signup and view all the answers

What is a subquery in SQL?

<p>A query nested inside another query. (D)</p> Signup and view all the answers

Flashcards

Database Management System (DBMS)

A system for managing and organizing data in a structured manner, providing controlled access and efficient data manipulation.

Relational Database

A database that organizes data into one or more tables in which data types are related to each other.

SQL (Structured Query Language)

A domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS).

Data Definition Language (DDL)

A category of SQL commands that define the database schema, including creating, altering, and dropping tables and databases.

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Data Manipulation Language (DML)

A category of SQL commands that allows users to manipulate data, including inserting, updating, deleting, and retrieving data.

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INSERT

An SQL command used to add new rows of data into a table.

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UPDATE

An SQL command used to modify existing data in a table.

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DELETE

An SQL command used to remove rows from a table.

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SELECT

An SQL command used to retrieve data from one or more tables.

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WHERE Clause

An SQL clause used to filter the rows returned by a SELECT statement based on a specified condition.

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Study Notes

  • Databases and Database Management Systems (DBMS) are surveyed.
  • Relational databases are understood.
  • SQL is introduced and its significance is covered

SQL Basics

  • SQL syntax and structure is defined
  • SQL command types include DDL, DML, DCL, and TCL

Data Definition Language (DDL)

  • DDL is a type of SQL command
  • Databases and tables are created using DDL
  • Table structures are modified with ALTER
  • Tables and databases are deleted with DROP
  • Data types in SQL are determined

Data Manipulation Language (DML)

  • DML is a type of SQL command
  • Data is inserted into tables using INSERT
  • Existing records are updated using UPDATE
  • Records are deleted using DELETE
  • Data is retrieved from tables using SELECT

Querying Data

  • The SELECT statement is utilized
  • Results are filtered with the WHERE clause
  • Results are ordered with ORDER BY
  • DISTINCT is used to eliminate duplicates

Functions and Expressions

  • Aggregate functions include COUNT, SUM, AVG, MIN, MAX
  • There are also string functions
  • Date and time functions exist
  • Mathematical functions are available

Joining Tables

  • Understanding the relationships between tables.
  • Inner Join
  • Outer Join (left, right, full)
  • Self Join

Subqueries

  • Subqueries are queries within queries
  • Subqueries are used in SELECT, INSERT, UPDATE, and DELETE statements
  • Correlated subqueries exist

Indexes and Constraints

  • Indexes are created and used
  • Primary key and foreign key constraints are used
  • Unique and check constraints are enforced
  • Default values are set

Views and Stored Procedures

  • Views are created and used
  • Stored procedures are introduced
  • Advantages of using views and stored procedures.

Transactions and Security

  • Transactions are understood
  • COMMIT and ROLLBACK are utilized for transaction control
  • Database security basics are covered

Practical Exercises

  • Hands-on SQL exercises and projects facilitate learning
  • Query writing and optimization techniques are practiced
  • Real-world case studies are reviewed

Conclusion and Next Steps

  • Advanced SQL topics are surveyed.
  • Resources for further learning are offered.

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