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Questions and Answers
What is the purpose of creating a domain in SQL?
What is the purpose of creating a domain in SQL?
Which of the following is NOT a basic constraint type in SQL?
Which of the following is NOT a basic constraint type in SQL?
In SQL, what does the CHECK clause do when specified on an attribute?
In SQL, what does the CHECK clause do when specified on an attribute?
What is the function of the PRIMARY KEY clause in SQL?
What is the function of the PRIMARY KEY clause in SQL?
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How can you specify that a certain attribute cannot accept NULL values in SQL?
How can you specify that a certain attribute cannot accept NULL values in SQL?
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What must every SQL statement end with?
What must every SQL statement end with?
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Which SQL standard introduced XML features?
Which SQL standard introduced XML features?
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Which of the following statements correctly describes base tables in SQL?
Which of the following statements correctly describes base tables in SQL?
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In SQL, what does the CREATE SCHEMA statement specify?
In SQL, what does the CREATE SCHEMA statement specify?
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What is a characteristic of virtual relations or views in SQL?
What is a characteristic of virtual relations or views in SQL?
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Which data type is NOT a basic numeric data type in SQL?
Which data type is NOT a basic numeric data type in SQL?
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Which term is used for a row in the relational model?
Which term is used for a row in the relational model?
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What does the DATE data type include in SQL?
What does the DATE data type include in SQL?
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What is the purpose of the CREATE TABLE command in SQL?
What is the purpose of the CREATE TABLE command in SQL?
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What are the basic components of an SQL schema?
What are the basic components of an SQL schema?
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Which attribute data type allows storage of boolean values in SQL?
Which attribute data type allows storage of boolean values in SQL?
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Which of the following describes the INTERVAL data type in SQL?
Which of the following describes the INTERVAL data type in SQL?
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Which of the following is NOT a type of constraint that can be specified in SQL?
Which of the following is NOT a type of constraint that can be specified in SQL?
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Which version of SQL is considered the current standard known as SQL-3?
Which version of SQL is considered the current standard known as SQL-3?
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Which SQL data type can be cast or converted into string formats for comparison?
Which SQL data type can be cast or converted into string formats for comparison?
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What type of string data type has a fixed length in SQL?
What type of string data type has a fixed length in SQL?
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Study Notes
Database Concepts
- SQL is a comprehensive language for relational database management.
- It covers data definition (creating tables), constraint specification, queries (retrieving data), and updates (modifying data).
Data Types and Domains
- Numeric: INTEGER, INT, SMALLINT, FLOAT, REAL, DOUBLE PRECISION
- Character string: CHAR(n), CHARACTER(n), VARCHAR(n), CHARACTER VARYING(n)
- Bit-string: BIT(n), BIT VARYING(n)
- Boolean: TRUE, FALSE, NULL
- Date: YYYY-MM-DD
- Timestamp: Includes date and time, with decimal fractions of seconds.
- INTERVAL: Relative time value.
- Domains: Named domains used for better readability and easier changing of the data type.
Constraints
-
Basic constraints:
- Key constraint
- Entity Integrity Constraint
- Referential integrity constraints
-
Attribute constraints:
- Default values
- NOT NULL constraint
- CHECK clause
-
Key and referential integrity constraints:
- PRIMARY KEY
- UNIQUE
- FOREIGN KEY
- Giving Names to Constraints: Using the keyword CONSTRAINT to name constraints.
SQL Statements: INSERT
- Used to add tuples to a relation.
- Attribute values must be listed in the same order as specified in CREATE TABLE.
- Can insert multiple tuples at once, using a query result as input.
- Bulk loading is possible using a similar method.
SQL Statements: DELETE
- Used to remove tuples from a relation.
- Includes a WHERE clause to specify which tuples to remove.
- Referential integrity is enforced.
SQL Statements: UPDATE
- Used to change attribute values of selected tuples.
- Includes a WHERE clause to specify which tuples to update.
- Calculations are possible in the SET clause.
Retrieval Queries
- SELECT: retrieves data.
- FROM: Specifies the table(s).
- WHERE: Filters the query results based on a condition.
- ORDER BY: Orders the results.
- Logical Comparison Operators: =, <, >, <=, >=, !=, and
- String Pattern Matching (LIKE): % and _ for wildcards.
- BETWEEN: specifies a range of values.
- Arithmetic operations are applicable within the SELECT statement.
- Aliases (and tuple variables): are used to name tables for clarity.
Important Concepts:
- Tables as Sets: SQL deals with tables as sets, not multisets.
- Ambiguous Attribute Names: Be clear which attribute you mean when duplicate names exist in different tables.
Additional Features
-
Schema and Catalog Concepts:
- Schema includes the structure of tables within the database.
- Catalog is a collection of schemas.
- Retrieval Query Block: The fundamental structure of retrieval queries in SQL involves SELECT, FROM, WHERE, and ORDER BY clauses.
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Description
This quiz covers essential database concepts, focusing on SQL language components such as data definition, data types, and constraints. Explore various numeric, character string, and date-time data types, along with integrity constraints crucial for relational database management.
