Convert XLSX to SQLite3

Working from a .xlsx file

A .xlsx file is OOXML - a zip of XML parts - and holds up to 1,048,576 rows per sheet. It also states its number formats explicitly, which is why more type information survives the trip out of .xlsx than out of any other spreadsheet format.

• →The workbook is opened for cached values only, so a formula cell converts as the number Excel last calculated for it. A file written by a script that never opened it in Excel can have those cells empty.
• →A column's number format is taken from the first data row that states one, so formatting only the header row tells the reader nothing about the column.
• →Accounting formats count as money even with no symbol in them: #,##0.00 is read as fixed-point, not as a plain number.

The .sqlite3 name and what carries over

The 3 in sqlite3 is the file format version and the name of the command-line tool, not a property of your conversion. One database file arrives, and the two things worth knowing about it are what it is called and what it leaves behind.

• →The file inside the zip is always database.sqlite, whichever spelling brought you to this page. Rename it to database.sqlite3, or to whatever a framework expects, once you have it - the header is what identifies it, never the extension.
• →An auto-increment column arrives holding all of its values and nothing that assigns new ones. No AUTOINCREMENT keyword is written, and the column is declared BIGINT rather than exactly INTEGER, so it is not an alias for the rowid either: rows you insert later have to supply their own key.
• →Only the rows are transactional. The very first CREATE TABLE runs in autocommit, and everything after it - that table's rows, and every later table - sits in one transaction that commits after the last row. A conversion that fails partway therefore leaves a file holding an empty shell of the first table and nothing else. You never receive that file: the zip is only assembled once the writer has returned.

Reading XLSX

• →Numbers, dates and booleans are read as Excel stored them, never converted to text and re-parsed.
• →Cell number formats are read out of .xlsx workbooks, so a column formatted as currency becomes a fixed-point decimal rather than a floating-point number — which is how money avoids acquiring a rounding tail. Legacy .xls is the exception: the xlrd path exposes no formats, so its currency columns come across as ordinary numbers.
• →A column formatted as a date becomes a date, not a timestamp at midnight; one formatted with a time keeps its time.
• →One sheet becomes one table. Empty sheets are skipped, and sheet names are sanitised for the target.

Writing SQLite3

• →Columns get real declared types rather than everything being TEXT.
• →Primary keys and NOT NULL constraints are preserved.
• →A money column is declared NUMERIC(10,2), but that declaration does not stop SQLite’s own numeric affinity from converting the inserted value into a float once it lands, so 19.99 can come back with a rounding tail. Pick the DuckDB target instead when the exact decimal has to survive.

Convert XLSX to something else

• MySQL
• PostgreSQL
• Oracle
• SQL Server
• DuckDB
• CSV

Convert something else to SQLite3

• CSV
• SQL dump
• DBF
• JSON
• XML
• Parquet
• DuckDB
• MS Access
• PostgreSQL backup