BLOB and binary types in MySQL - Time & Space Complexity

Time Complexity: BLOB and binary types

O(n)

Understanding Time Complexity

When working with BLOB and binary types in MySQL, it's important to understand how the time to read or write data grows as the data size increases.

We want to know how the operations scale when handling larger binary data.

Scenario Under Consideration

Analyze the time complexity of inserting and retrieving binary data using BLOB types.

INSERT INTO images (id, data) VALUES (1, LOAD_FILE('photo.jpg'));

SELECT data FROM images WHERE id = 1;
    

This code inserts a binary file into a BLOB column and then retrieves it by id.

Identify Repeating Operations

Look for repeated work inside these operations.

• Primary operation: Reading or writing the binary data byte by byte or in chunks.
• How many times: The operation repeats once for each byte of the binary data.

How Execution Grows With Input

The time to insert or retrieve grows as the size of the binary data grows.

Input Size (bytes)	Approx. Operations
10 KB	10,240 operations
100 KB	102,400 operations
1 MB	1,048,576 operations

Pattern observation: The operations increase directly with the size of the data.

Final Time Complexity

Time Complexity: O(n)

This means the time grows linearly with the size of the binary data being handled.

Common Mistake

[X] Wrong: "Reading or writing BLOB data takes the same time no matter how big the file is."

[OK] Correct: The time depends on the size of the data because each byte must be processed, so bigger files take longer.

Interview Connect

Understanding how binary data operations scale helps you explain performance in real applications that store images, videos, or files in databases.

Self-Check

What if we changed from BLOB to storing file paths as text? How would the time complexity of retrieval change?

Practice

1. Which MySQL data type is best suited for storing large binary files like images or videos?

easy

A. BLOB

B. VARCHAR

C. TEXT

D. INT

Solution

1. Step 1: Understand data types for binary storage

   BLOB is designed to store large binary data such as images or videos.

2. Step 2: Compare with other types

   VARCHAR and TEXT store text data, INT stores numbers, so they are not suitable for binary files.

3. Final Answer:

   BLOB -> Option A

4. Quick Check:

   Large binary data = BLOB [OK]

Hint: Large binary data? Choose BLOB type [OK]

Common Mistakes:

• Choosing VARCHAR or TEXT for binary data
• Using INT for storing files
• Confusing BLOB with text types

2. Which of the following is the correct way to declare a fixed-length binary column of 16 bytes in MySQL?

easy

A. BLOB(16)

B. VARBINARY(16)

C. BINARY(16)

D. TEXT(16)

Solution

1. Step 1: Identify fixed-length binary type

   BINARY(n) stores fixed-length binary data of n bytes.

2. Step 2: Check other options

   VARBINARY is variable-length, BLOB and TEXT are for large data, not fixed-length binary.

3. Final Answer:

   BINARY(16) -> Option C

4. Quick Check:

   Fixed-length binary = BINARY(n) [OK]

Hint: Fixed-length binary? Use BINARY(size) [OK]

Common Mistakes:

• Using VARBINARY for fixed-length data
• Trying to specify size with BLOB or TEXT
• Confusing TEXT with binary types

3. Given the table files(id INT, data BLOB), what will the following query return?

SELECT LENGTH(data) FROM files WHERE id = 1;

medium

A. The first byte of the 'data' column

B. The size in bytes of the binary data stored in 'data' for id 1

C. The number of characters in the 'data' column as text

D. An error because LENGTH() does not work on BLOB

Solution

1. Step 1: Understand LENGTH() on BLOB

   LENGTH() returns the number of bytes in the binary data stored in a BLOB column.

2. Step 2: Analyze the query

   The query selects LENGTH(data) for the row where id = 1, so it returns the size in bytes of that binary data.

3. Final Answer:

   The size in bytes of the binary data stored in 'data' for id 1 -> Option B

4. Quick Check:

   LENGTH(BLOB) = byte size [OK]

Hint: LENGTH() on BLOB returns byte size [OK]

Common Mistakes:

• Thinking LENGTH() counts characters in binary
• Expecting an error from LENGTH() on BLOB
• Confusing LENGTH() with SUBSTRING()

4. You wrote this table definition:

CREATE TABLE images (id INT, img BINARY(255));

But when inserting images larger than 100 bytes, data gets truncated. What is the problem?

medium

A. BINARY cannot store binary data, use TEXT instead

B. The id column should be AUTO_INCREMENT

C. You must use VARCHAR for binary data

D. BINARY(255) is fixed-length and pads or truncates data to 255 bytes

Solution

1. Step 1: Understand BINARY(n) behavior

   BINARY(n) stores fixed-length binary data of exactly n bytes, padding or truncating as needed.

2. Step 2: Identify truncation cause

   If inserted data is larger than 255 bytes, it will be truncated to fit fixed length.

3. Final Answer:

   BINARY(255) is fixed-length and pads or truncates data to 255 bytes -> Option D

4. Quick Check:

   Fixed-length truncates data > size [OK]

Hint: Fixed-length binary truncates data exceeding size [OK]

Common Mistakes:

• Thinking BINARY can store variable-length data
• Using VARCHAR for binary data
• Ignoring fixed-length padding/truncation

5. You want to store user profile pictures in a MySQL table with columns id INT and picture. You expect pictures up to 2MB. Which data type should you choose for picture and why?

hard

A. MEDIUMBLOB, because it supports up to 16MB of binary data

B. BINARY(2000000), because fixed-length is faster

C. VARCHAR(2000000), because it stores variable-length data

D. TEXT, because pictures are text data

Solution

1. Step 1: Check size requirements

   Pictures up to 2MB require a BLOB type that can hold at least 2 million bytes.

2. Step 2: Choose suitable BLOB type

   MEDIUMBLOB supports up to 16MB, enough for 2MB pictures. BINARY(2000000) is fixed-length and too large, VARCHAR and TEXT are for text, not binary.

3. Final Answer:

   MEDIUMBLOB, because it supports up to 16MB of binary data -> Option A

4. Quick Check:

   Large binary data > 64KB = MEDIUMBLOB [OK]

Hint: Use MEDIUMBLOB for binary data > 64KB [OK]

Common Mistakes:

• Using fixed-length BINARY for large data
• Choosing VARCHAR or TEXT for binary files
• Underestimating BLOB size limits