MySQL MCQs with answers Page - 4

Explanation:

The term CHARSET is commonly used as a synonym for character set, which refers to a collection of characters that can be used by a computer system or program. In the context of encoding, a CHARSET specifies the mapping of characters to their corresponding numeric values, such as in UTF-8 or ASCII.

• CHARSET is a widely recognized abbreviation and is used in various contexts, including HTML, HTTP headers, and databases.

Why the other options are incorrect:

• (B) CHCSET: This is not a commonly used abbreviation for character set.
• (C) CSET: Although it's a possible abbreviation, it is less standard and not widely used compared to CHARSET.
• (D) CHSET: Similarly, this is not a commonly accepted abbreviation for character set.

Thus, (A) CHARSET is the most widely recognized synonym for character set.

Explanation:

Post MySQL 5.5 (including MySQL 6.0 and beyond), the utf8 character set was replaced by a new character set called utf8mb4. The original utf8 character set in MySQL was capable of storing only up to 3 bytes per character, which was insufficient to store certain characters in the Unicode standard (e.g., some emoji and other characters outside the Basic Multilingual Plane).

The new utf8mb4 character set was introduced to support the full Unicode character set, using up to 4 bytes for each character, which allows it to store all possible Unicode characters, including those outside the Basic Multilingual Plane (BMP).

• utf8 (prior to MySQL 6.0) used 3 bytes for each character.
• utf8mb4 (introduced as a more complete UTF-8 encoding) uses 4 bytes for each character.

Thus, the correct answer to the question is (D) 4 bytes.

Explanation:

Prior to MySQL 6.0, the utf8 character set in MySQL was capable of storing up to 3 bytes per character. This was an implementation of UTF-8 encoding, but it had a limitation: it could only handle characters that fit within the Basic Multilingual Plane (BMP) of Unicode, which includes most characters, but not all.

In this earlier version of utf8, some characters (like certain emoji or less common scripts) could not be represented because they required more than 3 bytes. This limitation was addressed with the introduction of the utf8mb4 character set, which supports up to 4 bytes per character and allows the full range of Unicode characters.

Therefore, prior to MySQL 6.0, the utf8 character set used 3 bytes per character.

Explanation:

In UTF-8, UTF stands for Unicode Transformation Format. UTF-8 is a variable-width character encoding that represents each character as one to four bytes, depending on the character's Unicode code point.

• Unicode: Refers to the universal character encoding standard that includes characters from virtually all written languages in use today.
• Transformation Format: Refers to the method of encoding Unicode characters into sequences of bytes for storage or transmission.

So, UTF-8 is a specific encoding scheme that represents Unicode characters using one to four bytes, and "UTF" in this context stands for Unicode Transformation Format.

Why the other options are incorrect:

• (A) Unicode Transformation Formula: This is incorrect because the word "Formula" is not used in the official terminology.
• (B) Universal Transformation Formula: This is incorrect as it misrepresents the "Unicode" part of the standard.
• (D) Universal Transformation Format: While "Universal" might sound plausible, the correct term is "Unicode," not "Universal."

Thus, the correct term is (C) Unicode Transformation Format.

Explanation:

In MySQL, the SHOW VARIABLES statement is used to display the current system variables, including the character set and collation settings.

To check the current character set and collation for the server, you can run:

SHOW VARIABLES LIKE 'character_set%';

SHOW VARIABLES LIKE 'collation%';

This will return the character set and collation settings for various components like the server, client, connection, and database.

Why the other options are incorrect:

• (A) DISP VARIABLES: This is not a valid MySQL command.
• (B) SHOW CONSTRAINTS: This command is used to display constraints in the database, not character set or collation.
• (C) SHOW CONSTANTS: There is no SHOW CONSTANTS command in MySQL. It’s not valid.

Therefore, the correct statement to show the server’s current character set and collation settings is (D) SHOW VARIABLES.

Explanation:

The SQL statement:

SHOW COLLATION LIKE 'utf8%'

uses the SHOW COLLATION command to list all collations whose names begin with utf8. The % symbol is a wildcard character in SQL that matches any sequence of characters, including no characters at all. Therefore, the pattern 'utf8%' matches any collation names that start with "utf8."

For example, it could list collations like:

• utf8_general_ci
• utf8_unicode_ci
• utf8mb4_general_ci

These collations all start with utf8.

Why the other options are incorrect:

• (A) names ending in utf8%: This would match names ending in utf8 followed by any sequence of characters, but the % after utf8 means it can match anything starting with utf8, not just at the end.
• (C) names ending with utf8: This would be incorrect because utf8% matches names starting with utf8, not ending with it.
• (D) names containing utf8% anywhere: The % symbol at the end means the match is for names starting with utf8, not anywhere in the name.

Therefore, the correct answer is (B) names beginning with utf8.

Explanation:

In MySQL, the SHOW CHARACTER SETS statement is used to list all available character sets. It will display information about the character sets supported by the MySQL server, including their names and descriptions.

For example:

SHOW CHARACTER SETS;

This will return a list of character sets such as utf8, latin1, utf8mb4, and others available in the MySQL server.

Why the other options are incorrect:

• (B) SHOW COLLATIONS: This command lists the available collations in MySQL, not character sets.
• (C) SHOW CHARACTER SET: This is incorrect because there is no SHOW CHARACTER SET command in MySQL. The correct command is SHOW CHARACTER SETS.
• (D) SHOW COLLATION: Similar to (B), this command lists available collations, not character sets.

Thus, the correct command to find out which character sets are available is (A) SHOW CHARACTER SETS.

Explanation:

In SQL, the COLLATE clause is used to specify the collation for a string column, allowing you to sort string values according to a specific collation. Collations determine how string comparison and sorting are done (e.g., case sensitivity, accent sensitivity, etc.).

For example, if you want to sort a column name in a specific collation, you would use the COLLATE clause like this:

SELECT name 

FROM users 

ORDER BY name COLLATE utf8_general_ci;

This ensures that the string values are sorted according to the utf8_general_ci collation.

Why the other options are incorrect:

• (A) GROUP: This is part of the GROUP BY clause used for grouping rows in SQL, not for sorting by collation.
• (B) FILTER: This is not a valid SQL clause for sorting or collation. It's used in other contexts, such as with window functions in some database systems.
• (D) SORT: There's no SORT clause in SQL for sorting strings by collation. The sorting is done using ORDER BY.

So, the correct clause to use for sorting string values according to a specific collation is (C) COLLATE.

Explanation:

MySQL does provide support for Unicode, which allows it to store and manage text in multiple languages. Unicode support is achieved through character sets such as utf8 and utf8mb4. The utf8mb4 character set in MySQL, for example, supports the full range of Unicode characters, including emojis and other characters beyond the Basic Multilingual Plane (BMP).

• utf8: This character set supports most Unicode characters, but it is limited to 3 bytes per character.
• utf8mb4: This character set supports the full Unicode standard, using up to 4 bytes per character, which includes characters such as emojis and other supplementary characters.

Therefore, MySQL does support Unicode, and the correct answer is True.

Explanation:

In MySQL, a single character set can have multiple collations associated with it. A collation defines how strings are compared and sorted within that character set, taking into account factors like case sensitivity and accent sensitivity.

For example:

• The utf8 character set has several collations, such as:
  • utf8_general_ci (case-insensitive, accent-insensitive)
  • utf8_unicode_ci (case-insensitive, accent-insensitive, but with more accurate sorting rules for various languages)
  • utf8_bin (case-sensitive, binary comparison)

Thus, a single character set can have multiple collations, which is why the correct answer is (A) more than 1.