Final answer:
The SQL query fails to return results possibly because of a date format mismatch, absence of matching data, or typographical errors in column names or values.
Step-by-step explanation:
The SQL query SELECT * FROM sales WHERE product = 'Chair' AND transaction_date = '1/12/19' may not yield results due to several potential reasons. Firstly, ensure the format of the date in the transaction_date column matches the format provided in the query. Database systems have specific date formats, and mismatches will cause the query to return no results. Secondly, confirm that there are indeed records with the product 'Chair' and the given transaction date in the sales table. An absence of matching data will result in an empty result set. Lastly, verify that there are no typographical errors in the column names or the values provided, such as incorrect casing or additional spaces, as SQL is typically case-sensitive and precise with string comparisons.
The SQL query does not yield any results because the date format in the query does not match the date format in the database. The query specifies the date as '1/12/19', which is in the format mm/dd/yy. However, the date in the database may be stored in a different format, such as dd/mm/yy or yyyy-mm-dd.
To fix this issue, you need to ensure that the date format in the query matches the date format in the database. You can do this by either modifying the query to use the correct date format or by converting the date format in the database to match the format in the query.