Here are the limitations of SQL1 standard:
1) Use of subqueries is limited: As per the SQL1 standards, a subquery has to appear only on the right side of a comparison test in a WHERE clause.
2) No decision making capabilities in queries: In SQL1, there’s not very much options to have decision making capabilities in the queries. For example, if a two column report has to be generated from a database. It should show each sales office by its annual sales target or its year to date sales, whichever is larger. This would be a very complex query to write by using SQL1 standards.
3) Complex row expressions: SQL1 cannot handle complex row expressions.
4) Complex column expressions: SQL1 cannot handle complex column expressions.
5) No complex queries: It is very difficult in SQL1 to handle complex queries. For creating complex query each query needs to be written individually by breaking them into parts.