Column mapping with @Column in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @Column annotation in Spring Boot?

The @Column annotation maps a Java class field to a specific column in a database table. It helps customize column properties like name, length, and nullability.

beginner

How do you specify a custom column name using @Column?

Use the 'name' attribute inside @Column, for example: @Column(name = "user_email") maps the field to the 'user_email' column in the table.

beginner

What does setting nullable = false in @Column do?

It makes the database column NOT NULL, meaning the column must always have a value and cannot be left empty.

beginner

Can @Column control the length of a String column? How?

Yes, by setting the 'length' attribute, e.g., @Column(length = 100) limits the string column to 100 characters.

beginner

What happens if you omit the @Column annotation on a field?

Spring Boot uses default mapping: the field name becomes the column name, and default settings apply for length, nullability, etc.

Which attribute of @Column sets the database column name?

A name

B length

C nullable

D unique

The 'name' attribute specifies the exact column name in the database.

What does @Column(nullable = false) enforce?

A Column length is unlimited

B Column can be empty

C Column is unique

D Column must have a value

Setting nullable = false means the column cannot be empty (NOT NULL).

How do you limit a String column to 50 characters using @Column?

A @Column(length = 50)

B @Column(size = 50)

C @Column(max = 50)

D @Column(limit = 50)

The 'length' attribute controls the maximum size of a String column.

If you do not use @Column on a field, what happens?

A Field is ignored

B Error occurs

C Default column mapping applies

D Field becomes primary key

Without @Column, default mapping uses the field name as the column name.

Which @Column attribute ensures column values are unique?

A name

B unique

C length

D nullable

The 'unique' attribute enforces uniqueness of column values.

Explain how to use @Column to customize a database column in Spring Boot.

Think about how you control column name, size, and whether it can be empty.

Describe what happens if you omit the @Column annotation on a field in a Spring Boot entity.

Consider the default mapping rules Spring Boot applies.