MySQL：无法从SELECT语句中调用函数

Question

I have created a function called removeYear in SQL. The function is defined as:

CREATE FUNCTION removeYear(passedTitle CHAR(255), passedYear CHAR(100))
RETURNS CHAR(255) DETERMINISTIC

The function works properly. The problem is that I am unable to call it from within a SELECT statement using one of my column names. For example:

SELECT movieid, title
FROM movies
WHERE movieid = 40;

Works.

SELECT movieid, title, removeYear("bluh", movies.year)
FROM movies
WHERE movieid = 40;

Works.

SELECT movieid, title, removeYear(movies.title, movies.year)
FROM movies
WHERE movieid = 40;

Gives the following error: Error Code: 1054 Unknown column 'title' in 'field list' .

I have simply no idea what is causing this error. movies.title is a valid column. I have tried calling the function with every other column in my table, and those all work fine. For example:

SELECT movieid, title, removeYear(movies.movieid, movies.year)
FROM movies
WHERE movieid = 40;

Executes just fine.

EDIT: In my frustration, I decided to go over the 100+ lines of code comprising the function for the umpteenth time, finally spotting the single word in the code that was causing the error.

Just a single time in the entire block of code, I had accidentally written

title

Instead of

passedTitle

Whilst my problem is fixed, this still begs the question:

Does an SQL function share a namespace with the SELECT statement calling it?

Answer 1

Does an SQL function share a namespace with the SELECT statement calling it?

As per your function signature definition

CREATE FUNCTION removeYear(passedTitle CHAR(255), passedYear CHAR(100))
RETURNS CHAR(255) DETERMINISTIC

Value of first parameter is always identified within the function body using its name passedTitle only.

And this is applicable to any parameter or variable declared defined within any stored procedure.

And hence if you use title as name for the first parameter over its defined name passedTitle in the signature, engine won't recognise it runtime and throws an error.