Is "SET CHARACTER SET utf8" Necessary in PDO with "PDO::MYSQL_ATTR_INIT_COMMAND"?

In PHP and MySQL, "SET NAMES utf8" and "SET CHARACTER SET utf8" are typically used when working with UTF-8 encoding. However, when using PDO, the "PDO::MYSQL_ATTR_INIT_COMMAND" parameter limits us to a single query. Therefore, it's essential to consider if "SET CHARACTER SET utf8" is necessary in this context.

Impact of "SET CHARACTER SET utf8" on Connection Settings

Using "SET CHARACTER SET utf8" after "SET NAMES utf8" will reset the "character_set_connection" and "collation_connection" to the database's default settings ("@@character_set_database" and "@@collation_database").

Difference between "SET NAMES" and "SET CHARACTER SET"

"SET NAMES x" affects:

• "character_set_client"
• "character_set_results"
• "character_set_connection"

"SET CHARACTER SET x" affects:

• "character_set_client"
• "character_set_results"
• "collation_connection" (but also internally sets "character_set_connection")

Character Encoding/Transcoding Process

MySQL processes queries and results through multiple transcoding steps:

1. Converts incoming query from "character_set_client" to "character_set_connection"
2. Compares strings (columns vs. literals) using "column collation"
3. Builds result set in "character_set_results"

Significance of Default Database Character Set

If the database's default character set is not UTF-8, using "SET CHARACTER SET utf8" may not fully enable UTF-8 support. This is because step 3 of the transcoding process might result in data loss if the column collation is not UTF-8 compatible.

Conclusion

In general, "SET NAMES utf8" is the preferred method for handling character set issues. Setting the MySQL server variables in "my.cnf" can avoid the performance overhead of unnecessary SET commands on every connection.