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 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 changes when you convert PDF to SQL
Every character in a text-based PDF carries its position on the page. Characters sharing a baseline are one row. Columns are found from the vertical strips no character ever occupies, which is why extraction works cleanly on a document laid out with spacing and badly on one laid out with ruled lines. A header repeated at the top of each page is detected and dropped rather than landing in the middle of the data.
String values are escaped by doubling any single quote. Statements are written in batches so a large table does not become one statement megabytes long, which many clients refuse. Ask for CREATE TABLE as well and column types are inferred: a column stays INT until a value does not fit, then widens to DECIMAL, then to VARCHAR.
What carries over from PDF to SQL
One property of the PDF has no home in SQL, and it is worth knowing which before you convert.
SQL wants a type for each column, and PDF does not record one, so each column is typed from what its values look like. A column of digits that should stay text - a zip code, a phone number, a leading-zero id - is the usual thing to check afterwards.
SQL marks its header cells differently from its data cells, so the first row is written with that marker.
Anything visual in the PDF - weight, alignment, colour, column widths - has no counterpart in SQL and is dropped. The values are what survives.
The result can be read a record at a time, and appended to by adding to the end of it. That is worth having for a table too large to hold in memory, and it means a SQL file that is cut off part way through still gives you every record before the cut.
This is the direction that recovers structure: PDF has no table in it to read, only an arrangement that looks like one, so the rows and columns are inferred rather than read.