Convert XLS to SQLite3

Working from a .xls file

A .xls file is BIFF8, the binary format Excel used through 2003. Its hard ceiling is 65,536 rows and 256 columns per sheet, which is the single most common reason a spreadsheet has to become a database: the data outgrew the file format, not the machine.

• →The .xls path reads through pandas and xlrd, which does not expose cell number formats - so a column formatted as currency arrives as a floating-point number rather than a fixed-point decimal.
• →The preview screen is where to correct that: retype the column to decimal before converting, or re-save the workbook as .xlsx, which does carry its formats through.
• →If your file is near the 65,536-row limit, check whether it was already truncated when it was saved - the conversion moves what is in the file, and cannot recover rows Excel dropped.

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 XLS

• →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 XLS 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