The reason why you are getting an error message when using UNION in your SQL code is that UNION should be used between two SELECT statements to combine the results of both queries into a single result set. However, in your code, you are using UNION after the first SELECT statement, which is not a valid syntax.To fix the issue and add more rows to your abcd table using UNION, you should use the following code instead:
INSERT INTO abcd(name)
SELECT 'aaaaa'
UNION
SELECT 'bbbb';
This code will select two rows, 'aaaaa' and 'bbbb', and combine them into a single result set using UNION, which will then be inserted into the abcd table.
Note that the SELECT statements used in the UNION must have the same number of columns and compatible data types. In this case, both SELECT statements only select one column, 'aaaaa' and 'bbbb', which are both strings, so they are compatible and can be combined using UNION.