What SQL is
SQL here means the statements that move a table into a database: INSERT INTO with a VALUES list, and optionally the CREATE TABLE that defines the columns.
Anyone seeding a database, moving a spreadsheet into an application, or writing a migration.
What PDF is
PDF describes a page: glyphs at coordinates, not rows and columns. A table in a PDF is a visual arrangement, not a data structure.
Reports, invoices, statements and anything sent to be read rather than processed.
What changes when you convert SQL to PDF
Column names come from the INSERT column list, or from a CREATE TABLE if one is present. Quoted strings are unquoted, doubled quotes are collapsed, and NULL becomes an empty cell.
The table is drawn into a paginated document with the header repeated on every page, so a long table stays readable past page one. Page size, orientation and font size are all adjustable.
What carries over from SQL to PDF
SQL records 5 things about a table that PDF has no way to hold.
SQL knows which of its values are numbers. PDF keeps only their appearance, so nothing downstream can sort or sum them without someone reading them back off the page first.
An empty cell and a missing one are the same thing in PDF, so a null and an empty string in the SQL both come out blank and can no longer be told apart.
Nothing in PDF records that the first row is a header. It is drawn at the top and looks like one, which is all that is left of the distinction.
SQL can be read one record at a time. PDF has to be complete before it means anything, so the whole table is held in memory while it is written and a file that gets cut off part way through is not partly usable - it is unusable.
PDF is the end of the line for this data. Reading the table back out of it is a separate and much harder problem than writing it, so keep the SQL if you will need the values again.