How to check if a value is a number in SQLite

Question

I have a column that contains numbers and other string values (like \"?\", \"???\", etc.)

Is it possible to add an \"is number\" condition to the where clause in SQL

Answer 1

For integer strings, test whether the roundtrip CAST matches the original string:

SELECT * FROM mytable WHERE cast(cast(mycolumn AS INTEGER) AS TEXT) = mycolumn

For consistently-formatted real strings (for example, currency):

SELECT * FROM mytable WHERE printf("%.2f", cast(mycolumn AS REAL)) = mycolumn

Input values:

• Can't have leading zeroes
• Must format negatives as -number rather than (number).