Python Lesson 25: MySQL WHERE Clause

Study Notes

WHERE Clause: Use to filter selections based on specified conditions when querying records.
Wildcard Characters: The % symbol acts as a wildcard to match any string of characters.
SQL Injection Prevention: Escape user-provided query values to secure against SQL injection attacks.
mysql.connector Module: Contains methods to safely escape query values to mitigate SQL injection risks.

ORDER BY Statement: Sorts query results, ascending by default. Use DESC for descending order.
DELETE FROM Statement: Removes records from a table. Always use a WHERE clause to specify which records to delete; omitting it deletes all records.
mydb.commit(): Essential to make changes permanent in the database after a delete operation.

DROP TABLE Statement: Deletes an existing table from the database.
IF EXISTS Clause: Prevents errors from attempting to drop a non-existent table.

UPDATE Statement: Modifies existing records in a table. Always include a WHERE clause to prevent updating all records.
correct use of mydb.commit(): Ensures that changes made by the UPDATE statement are saved in the database.

Try-Except Block: Use try to test code for errors; except to handle exceptions. A finally block executes code regardless of the try-except result.
Common Exceptions: Includes NameError, AttributeError, KeyError, and ZeroDivisionError, among others.
Using Else: Allows defining a code block that runs if no errors occur in the try block.
Raising Exceptions: Utilize raise to throw exceptions deliberately when certain conditions are met.

Definition: Sets are unordered, unindexed collections denoted by curly brackets.
Accessing Items: Items can't be accessed via indices but can be checked for presence using the in keyword.
Adding and Removing Items: Use add() to include an item; remove() or discard() to delete an item. pop() removes an arbitrary item.
Joining Sets: Use union() to create a new set with combined elements or update() to insert items into an existing set.

Uniqueness: Sets automatically discard duplicates.
Membership Testing: Fast checks for element existence compared to lists.
Set Operations: Support union, intersection, and difference operations for comparative analyses of data.
Mutability of Set: Sets are mutable, but their contents must be immutable types, such as strings and tuples.

Downloading PyCharm: Available online; check “Update PATH Variable” during installation.
Creating a New Project: Navigate through File > New Project, name it, and click “Create.”
Running Python Scripts: Right-click on the project file to create a new Python file. Use Run > Run to execute scripts.