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Questions and Answers
What is the primary function of DDL in SQL?
What is the primary function of DDL in SQL?
- Grants user privileges for database access
- Manipulates existing data within a database
- Retrieves data from multiple tables
- Defines the structure of a database (correct)
Which of the following is NOT an example of a DML statement?
Which of the following is NOT an example of a DML statement?
- INSERT INTO
- UPDATE
- DELETE FROM
- CREATE TABLE (correct)
What does DML stand for in SQL?
What does DML stand for in SQL?
- Data Modification Logic
- Data Measurement Language
- Data Manipulation Language (correct)
- Database Management Layer
Which of the following operations is performed by DDL?
Which of the following operations is performed by DDL?
What purpose does the DELETE FROM statement serve in SQL?
What purpose does the DELETE FROM statement serve in SQL?
Which SQL statement is used to save changes made in a transaction?
Which SQL statement is used to save changes made in a transaction?
Which operation is not a typical use of DML?
Which operation is not a typical use of DML?
In the context of SQL, what is a subquery?
In the context of SQL, what is a subquery?
What does SQL primarily stand for?
What does SQL primarily stand for?
Which of the following actions can SQL NOT perform?
Which of the following actions can SQL NOT perform?
Which of the following best describes RDBMS?
Which of the following best describes RDBMS?
What is a field in the context of a database table?
What is a field in the context of a database table?
Which of the following statements is an example of DDL in SQL?
Which of the following statements is an example of DDL in SQL?
What does a row represent in a relational database?
What does a row represent in a relational database?
What is the primary purpose of the CREATE INDEX statement in SQL?
What is the primary purpose of the CREATE INDEX statement in SQL?
Which of the following is NOT an attribute of the Student_table?
Which of the following is NOT an attribute of the Student_table?
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Study Notes
Introduction to SQL
- SQL (Structured Query Language) accesses and manipulates databases.
- SQL executes queries, retrieves, inserts, updates, and deletes database records.
- SQL creates and modifies databases, tables, stored procedures, views, and permissions.
Relational Database Management Systems (RDBMS)
- RDBMS is the foundation for SQL and modern database systems (MS SQL Server, IBM DB2, Oracle, MySQL, Microsoft Access).
- Data in RDBMS is stored in tables (collections of related data entries with columns and rows).
- Tables contain fields (columns maintaining specific information per record).
- Records (rows) are individual table entries.
- Columns (vertical entities) contain information associated with a specific field.
- Attributes (columns/fields) represent characteristics of data stored in a table.
- Rows, also called records or tuples, represent single data items in a table.
Data Definition Language (DDL)
- DDL defines database structure (creating, modifying, deleting tables, columns, indexes, etc.).
CREATE TABLE: Creates a new table.ALTER TABLE: Modifies an existing table (adding, dropping, or modifying columns).DROP TABLE: Deletes an existing table.CREATE INDEX: Creates a table column index for better query performance.DROP INDEX: Deletes an existing table index.- DDL statements are executed before data insertion to ensure proper database structure.
Data Manipulation Language (DML)
- DML manipulates data within a database (inserting, updating, deleting data).
INSERT INTO: Inserts new rows.UPDATE: Modifies existing rows.DELETE FROM: Deletes existing rows.- DML statements are executed after defining database structure with DDL. They populate and modify the data.
DDL vs. DML Comparison
- DDL (Data Definition Language): Defines database structure; creates, modifies, and deletes database objects (tables, indexes, views, constraints). Examples:
CREATE TABLE,ALTER TABLE,DROP TABLE,CREATE INDEX,DROP INDEX. - DML (Data Manipulation Language): Manipulates database data; inserts, updates, and deletes data from tables. Examples:
INSERT INTO,UPDATE,DELETE FROM.
Additional SQL Statements
GRANT: Grants user privileges.REVOKE: Revokes user privileges.COMMIT: Saves transaction changes.ROLLBACK: Undoes transaction changes.
Other SQL Features
- Joins: Combine data from multiple tables.
- Subqueries: Embed queries within other queries.
- Aggregates: Perform calculations on data (e.g.,
SUM,AVERAGE,COUNT).
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