SQL Basics Practice Test

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• Which statement creates a simple view named recent_orders showing orders from the last 30 days?
• SQL operator that returns true when the value is NULL and false otherwise
• The three main stages of normalization are collectively known as what?
• How do you sort employees by hire_date descending?
• Which clause lists the tables that contain the fields in the SELECT clause?
• Which aggregate function counts the number of non-null values in a column per group?
• Which acronym represents the four properties of a database transaction?
• Which term is a clause that indicates the column to edit?
• How do you find products whose name starts with 'App'?
• How do you concatenate first_name and last_name with a space in between?
• Where is the DISTINCT qualifier placed in a SELECT statement?
• Intermediate table to store a relationship where more than one row of T1 refers to more than one row of T2.
• Which SQL statement removes the table named old_data from the database?
• Which operator returns rows from the first query not present in the second query?
• Which term describes a virtual table that presents data as a table but does not store its own data?
• Which operator removes duplicates when combining results from two SELECT statements?
• Operator that returns true if the value on the left is greater than or equal to the value on the right.
• Which of the following creates a table with an inline primary key for id?
• Which statement creates an index on orders(customer_id) with the name idx_orders_customer_id?
• Which aggregate function returns the minimum value in a column, excluding NULLs?
• Which qualifier returns only unique values in a result set?
• Which data type stores fixed-length character values?
• How do you select first_name and last_name from employees and alias the column last_name as surname in the result?
• How do you return unique city values from a table customers?
• What language defines the access rights to data?
• Which concept defines the three boolean values SQL uses: TRUE, FALSE, and UNKNOWN?
• A construct containing copies of original values and backreferences to their original rows. Not part of the SQL standard.
• All queries begin with which command?
• Which statement accurately describes First Normal Form as presented?
• In DDL, how do you declare a column as the primary key?
• Which keyword sorts values in descending order?
• Which combination correctly starts a transaction and then commits it?
• How do you count the number of orders per customer?
• Which clause lists the fields that are not summarized in the SELECT clause when using aggregate functions?
• How do you extract the year from a date column named order_date?
• A data file that has no structured relationships between its records is known as a
• In a relational table, what is the smallest unit of data?
• What term refers to a special type of stored procedure that executes automatically in response to events and is associated with a specific table?
• How do you find records where phone is not provided (NULL) in customers?
• Which language retrieves and manipulates data (for example, SELECT, INSERT, DELETE)?
• What term describes a property used to characterize data items of entities, such as datatype and size?
• Which expression would you use to filter orders within the last 30 days relative to today?
• Which statement creates an index on orders(customer_id) with the name idx_orders_customer_id?
• How do you alias a table and a column in a SELECT?
• How do you return orders with customer details using an inner join between orders and customers on customer_id?
• A group of attributes describing the structure of entities is called what?
• Which term refers to the name of the table the command is applied to?
• In a JOIN, what clause specifies how rows from two tables are matched?
• Which normal form eliminates partial dependency of non-key attributes on the primary key?
• Which statement retrieves all columns from a table named orders?
• What is the process of organizing data to minimize redundancy and remove ambiguity by separating a DB into tables and defining relationships?
• Which data type stores both date and time?
• How do you select a customer's total orders using a scalar subquery in the SELECT list?
• Which query returns customers whose average order amount exceeds 100?
• Which SQL statement creates a new table?
• A language element which specifies a non arithmetic condition Ex. [NOT] IN, [NOT] LIKE
• In a many-to-many relationship, the rows of the junction table contain the primary keys of T1 and T2 as values.
• Which clause is used to filter groups after a GROUP BY based on a condition on aggregates?
• When using UNION to combine two SELECT statements, which condition must hold?
• Which operation returns only rows that appear in both result sets?
• Which property ensures that a transaction is fully completed or fully rolled back?
• Which aggregate function calculates the average value?
• Which data type stores fixed-length character values?
• In the numeral system using digits 0-9 and letters A-F, which system is described?
• Which syntax assigns an alias to a table in the FROM clause?
• Which clause is used to filter rows in query results?
• Write a query to fetch all orders with status = 'shipped'.
• Operator that returns true if the value on the left is larger than the value on the right.
• In the time format HH:MM:SS[.sf], what does the part in brackets represent?
• How do you replace NULL with a default value for a column in a SELECT?
• Which operator would you use to compute the total numeric value of a column, ignoring NULLs?
• Which principle states that completed transactions should remain stable/permanent even during system failure?
• How do you include all customers and their orders, even if a customer has none?
• Which operation is used to retrieve data by listing the fields to include?
• Which term refers to a keyword that represents an action or modifies an action, typically a verb or adverb?
• Which operation changes the structure of an existing table?
• Which normal form is defined as No duplicate information permitted; if two tables require a common field, that common field's information should be separated into a different table?
• What term refers to a virtual table defined by a query that references real tables?
• What term describes a name used to identify a database object, such as a field?
• How do you cast a string date '2020-01-01' to a DATE type?
• Which statement describes INNER JOIN behavior?
• What is the database system catalog that stores metadata about tables, views, and constraints?
• What is the difference between COUNT(*) and COUNT(column_name) when counting rows with NULLs?
• Which concept refers to a group of SQL statements that are treated as a single unit of work, which either all succeed or fail?
• What term describes an expression that evaluates to true or false?
• What term describes a set of rows of a certain entity-type, i.e., all rows share the same structure?
• Which clause sets a default value for a column named status to 'active'?
• What is the purpose of the CAST function?
• Which aggregate function returns the count of a column and includes NULL values when used with an asterisk?
• Used to temporarily rename a column or a column heading.
• What is the effect of ORDER BY hire_date DESC in a query?
• What format is described by 'YYYY-MM-DD' for dates?
• Which statement would count the number of orders per customer using a GROUP BY clause?
• In 1NF, which property describes the indivisibility of each value in a column?
• Which statement describes a scalar subquery in the SELECT clause?
• What is the primary goal of normalization in a relational database?
• Which operator returns distinct results when combining two result sets?
• Which SQL statement changes an existing table?
• NULL is an example of which type of value that does not change?
• Which database object points to a currently selected set of records and can be acted on as a group in many languages?
• Which construct describes a non arithmetic condition such as NOT IN or NOT LIKE?
• How do you declare a foreign key referencing another_table(id)?
• Which SQL statement edits a row in a table?
• In relational database terminology, a value that does not change, such as a number or NULL, is called a ...
• Which identifier denotes descending order in a sort operation?
• Which term describes a reference between two entities that depends on the values of the entities?
• Which statement creates a table named products with id as integer primary key and name as varchar(100) not null?
• Which SQL statement adds a new row to a table?
• How do you filter groups to those with more than 5 orders?
• In some SQL dialects, how can you handle NULL-safe equality checks in predicates?
• Which language defines the logical and physical design of a database (for example, CREATE TABLE)?
• Which symbol denotes a single-line comment in SQL-like syntax?
• Is the data type for a column that indicates text
• Which statement counts only non-null values in a column?
• A block whose content has changed memory, but is still not written to disk.
• Which data type is used to store strings with a specified maximum length?
• What term describes a single record in a table with exactly one value for each column?
• How do you check if a customer has any orders using EXISTS?
• In storage terms, what is a mass storage structure that contains rows or tables called?
• Which operator returns true if the values on either side are not equal to each other?
• How do you select rows where country is one of 'USA', 'Canada', or 'UK'?
• Which notation denotes a multi-line comment?
• Which query includes all orders and their customers, even if an order has no customer (rare scenario)?
• Which property ensures that concurrent transactions do not interfere with each other?
• How do you add a new column email VARCHAR(255) to a table users?
• Which term describes a fast-access structure that holds copies of original values and is not part of the SQL standard?
• Which clause or keyword is used to provide the list of values to insert into a table?
• Operator that returns true if the value on the left is smaller than the value on the right.
• Which sequence begins a transaction and then commits it?
• What is the term for a single data item located at the intersection of a row and a column?
• What is the primary idea of First Normal Form (1NF) in relational databases?
• What is the virtual table that contains only its definition and no real data, defined by a query over real tables?
• Which clause returns unique values for a column in a SELECT statement?
• What term describes a group of SQL statements that are executed as a single atomic unit?
• Which aggregate function returns the sum of values in a numeric column, excluding NULLs?
• A reference between two different or the same entity. Based upon the values of the entities.
• Which clause specifies how to sort the results of a query?
• Which query structure returns rows from customers where the id appears in the customer_id column of orders?
• Which aggregate function returns the maximum value in a column, excluding NULLs?
• Which data type is used to store binary data?
• In SQL, which concept allows you to assign a temporary name to a column or expression in a query?
• Which SQL statement queries data from a table?
• What is the term for a combination of identifiers, operators, constants and functions that evaluates to a single value?
• Which function returns the current date in many SQL dialects?
• Is a clause that lets you add a new column to a table.
• What is a common block comment notation used in many programming languages?
• What are the three main stages of normalization collectively called?
• Which term is a clause that indicates the data being inserted?
• Which operator would you use to compute the maximum numeric value in a column, ignoring NULLs?
• What is a correlated subquery?
• Which time format includes an optional fractional part?
• Which pattern returns customers whose id matches any customer_id in orders?
• In the hexadecimal number system, which characters are used to represent values 10-15?
• Which SQL statement deletes rows from a table? (Is a clause)
• Which statement removes all rows from the table old_data but keeps the table structure?
• Which term describes a constraint that holds a unique value identifying each record and may be composed of multiple fields?
• Which operator checks for NULL values in a condition?
• Which term refers to a data file with no relational structure among its records?
• Which qualifier returns all values by default?
• Which aggregate function returns the average value for a numeric column, excluding NULLs?
• Which operator checks if the left value is less than or equal to the right?
• Which data type would you use to store text in a column?
• A combination of operands and operators that yields a value for use in a query is called a
• Which SQL operator tests for the existence of rows returned by a subquery?
• Which term describes the fundamental unit of data that characterizes an entity, such as its datatype and size?
• Which data type stores variable-length character values?
• Which ACID property ensures that a transaction is all-or-nothing?
• Which query selects records from tickets where (status = 'open' AND priority = 'high') OR (status = 'new')?
• Which term describes a relationship or connection between two entities that can be a part of data modeling and is based on the values of the entities?
• In a database, which concept represents a single row within a table?
• In SQL, a language element that is part of a statement is called a
• Operator that returns true if the value on the left is less than or equal to the value on the right.
• Which operator returns true if the values on either side are equal to each other?
• Which data type is used to store binary data?
• How do you return only the first 10 rows from a query in PostgreSQL/MySQL?
• Which term is a special stored procedure that automatically runs in response to events on a table?
• Which operator lets you combine two SELECT statements into one, requiring the same number of output fields in the same order?
• Which mechanism allows rows of a table to be acted on at one time?
• Which SQL command would you issue to revert all uncommitted changes in the current transaction?
• Which syntax limits the number of rows to 10 in PostgreSQL/MySQL?
• Which description best defines a correlated subquery?
• Which construct defines higher-level rules for data items, including nullability and keys?
• Which clause imposes conditions on the fields that are summarized in the SELECT statement?
• Which operator compares if the left value is greater than or equal to the right?
• Which term describes a key field that identifies records in a table by matching a primary key in a different table?
• What is the result of a CROSS JOIN between two tables?
• Which SQL statement retrieves all columns from a table named customers?
• How do you get sales between 100 and 500 inclusive?
• In a relational database, a complete set of information presented in a table, with each row representing a single item, is called a
• Which operator checks for inequality (not equal) between two values?
• What does RDMS stand for?
• Which SQL command cancels the proposed changes in a pending transaction and marks the end of the transaction?
• Which property ensures transitions from one valid state to another valid state?
• Which data type stores only the time of day without a date?
• How do you ensure a column cannot contain NULL values at creation time?
• Which data type is used to store date values in the format year-month-day?
• Which keyword is used to define a default value for a column in a DDL statement?
• Which constraint enforces referential integrity by linking a column to a primary key in another table?
• Which statement fragment is used to add a new column to an existing table?
• Which clause specifies field criteria that must be met by each record to be included in the results?
• How do you get the length of a string in many SQL dialects?
• Which data type stores variable-length character values?
• An identifiable object like employee or department is an instance of which type?
• Which SQL command marks the finalization of a database transaction?
• Which database concept holds a unique value identifying each record and can be composed of multiple fields?
• Which CASE expression assigns 'high' for score > 80, 'medium' for >=50, else 'low'?
• Which is the correct syntax to modify an existing table by adding a new column?
• Which operation adds a new row to a table?