10 Questions
What is the purpose of the LIKE operator?
To search for a specified pattern in a WHERE clause
What does the IN operator allow you to do?
Specify multiple values in a WHERE clause
Which of the following is NOT an aggregate function?
LIKE()
What does the SUM() function do?
Calculates the sum of all values in a column
What does the AS keyword do in SQL?
Gives a temporary column name
Which aggregate function returns the maximum value of a column?
MAX()
What is the data dictionary used for?
To store metadata about the structure of a database
Which aggregate function calculates the average value of a column?
AVG()
What is the purpose of arithmetic operations in SQL?
To perform calculations on column values
Which of the following is NOT a valid aggregate function?
LIKE()
Study Notes
Data Dictionary
- Describes the structure of the whole database
- Organized in a spreadsheet format
- Includes the names and descriptions of the tables and the fields contained in each table along with information of the data type, field length
- Provides metadata, or information about data
- No one set standard in terms of layout or information
Entity-Relationship Modeling
- A separate table is created for each entity of the database
Constraints
- Used to specify rules for the data in a table
- Ensure the accuracy and reliability of the data
- Types of constraints:
- PRIMARY KEY: column that uniquely identifies each row in the table
- FOREIGN KEY: column that refers to the primary key in another table, relates two tables
- UNIQUE: ensure that all the values in a column are unique/different
- NOT NULL: ensure that a column cannot have a NULL value
- DEFAULT: set a default value for a column when no value is specified
- AUTO_INCREMENT: allows a unique number to be generated automatically when a new record is inserted into a table
Auto-Increment
- Allows a unique number to be generated automatically when a new record is inserted into a table
- Starting value for AUTO_INCREMENT is 1, and it will increment by 1 for each new record
- Useful for generating a unique primary key for each new record inserted into a table
SQL - WHERE Clause
- Used to extract only those records that fulfill a specified criteria
- Filter/search data
- Operators:
- Arithmetic Operators (+, -, *, /, %)
- Comparison Operators (=, <>, !=, etc.)
- Logical Operators (AND, OR, NOT)
- BETWEEN: selects values within a range
- IN: performs membership check
- LIKE: searches for a specified pattern
Aggregate Functions
- SUM(): sum of all the values in a column
- MAX(): maximum value of a column
- MIN(): minimum value of a column
- AVG(): average value of a column
Learn about the data dictionary, which describes the database structure in a spreadsheet format. It includes table and field names, data types, and more. Understand its role in providing metadata about data.
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