Read data from one column, Excel will check first 8 rows (Default Value)'s format. If first 8 rows are number, and row 9 is string, the string value will missing.
1. Add "IMEX=1" to connection string. 2. Change the key value in register.
Details: Check the following registry settings for the *machine*:
Hkey_Local_Machine/Software/Microsoft/Jet/4.0/Engines/Excel/TypeGuessRows Hkey_Local_Machine/Software/Microsoft/Jet/4.0/Engines/Excel/ImportMixedTypes
TypeGuessRows: setting the value to 0 (zero) will force ADO to scan all column values before choosing the appropriate data type.
ImportMixedTypes: should be set to value 'Text' i.e. import mixed-type columns as text:
Using IMEX=1 in the connection string (as you have done) ensures the registry setting is applied.