Database Schema, Relationships, and SQL Fundamentals for Students

What is the difference between Char and VarChar?

String lengths are fixed in Char.

How do you capture a recursive relationship in a relation schema?

The primary key is also identified as a foreign key.

What is the key for an associative entity in the relational model schema?

The key consists of the primary keys of the two related tables.

How is a one-to-many relationship implemented in a database schema?

The key of the one class becomes a foreign key in the many class.

In transforming a recursive relationship to the relational model, a foreign key is created that references what?

Its own relation.

What is the relational model concept equivalent to a many-to-many relationship?

A bridge table.

What SQL data type is used for strings?

VarChar.

Which of the following is NOT a valid default action for a foreign key on delete?

Remove.

What is the relational model concept equivalent to an attribute?

An attribute.

How are keys transformed to capture a one-to-one relationship?

The primary key of one class becomes a foreign key in the related class.

What is the relational model concept equivalent to an object entity?

A relation.

To make changes to a table definition, which command is used?

ALTER.

How is a many-to-many relationship implemented in a schema?

A new table is created with foreign keys of both classes.

What does Numeric(8,2) mean?

8 digits, 2 of them to the right of the decimal.

To remove a table from the database schema definition, which command is used?

DROP.

What is the second name for a table in the FROM clause called?

An alias.

What is the maximum number of tables that can be joined?

There is no maximum.

When are conditions connected by AND true?

Only when both conditions are true.

What clause gives the condition for selecting rows?

WHERE.

What SQL statement is used to enter new rows?

INSERT.

What clause identifies which tables the query accesses?

FROM.

In what order do SQL SELECT clauses run?

FROM, WHERE, SELECT, ORDER BY.

What does * in SQL SELECT mean?

List all columns.

What is the minimum number of clauses in a SELECT statement?

2.

What is the first column listed in ORDER BY?

The primary sort key.

What is the process of linking records across tables called?

Joining.

What clause specifies which columns to list?

SELECT.

What is a column whose value is always unique called?

A key.

What clause specifies how rows should be sorted?

ORDER BY.

When are conditions connected by OR true?

When either condition is true.

What is a doctor not allowed to view some records considered?

Not authorized.

What is the term for concurrent updates causing data loss?

Lost update problem.

What is NOT part of a viable backup/recovery process?

Periodic freezing of all transactions.

What is another name for symmetric encryption?

Single-key encryption.

What is the process of applying change logs to recover lost activity called?

Database restore and rerun.

What is reading outdated data called?

Inconsistent read problem.

What is determining who is requesting access called?

Authentication.

What is the plan to fix a lost or damaged database called?

Disaster recovery plan.

What is determining what actions are allowed called?

Authorization.

What does authorization validate?

A person's permissions.

What is using backups to restore the database to a point in time called?

Database restore and rerun.

What is a backup of only part of the database called?

Partial backup.

What type of backup requires all activity to stop?

Cold backup.

What occurs first when accessing a database?

Authentication, then authorization.

How is data hidden from being human readable?

By encrypting the data.