In formal SQL language definition, which of the following grammar productions are valid elements of the SQL syntax?

Introduction / Context:
The SQL language is defined in the standard using a formal grammar. That grammar uses productions of the form nonterminal ::= expansion to describe how legal SQL statements can be composed. Understanding that terms like base-table-identifier, base-table-name, and boolean-primary come from the SQL grammar helps you appreciate that SQL has a precise, well structured definition. Examination questions sometimes show such productions and ask you to identify which are real elements of the SQL syntax rather than random phrases.

Given Data / Assumptions:

• The notation nonterminal ::= expansion represents a grammar rule.
• base-table-identifier is meant to represent a user defined name of a base table.
• base-table-name is another nonterminal that builds on base-table-identifier.
• boolean-primary and comparison-predicate are grammar terms related to expressions that evaluate to true or false.
• We assume these productions are taken from a simplified view of the SQL standard grammar.

Concept / Approach:
In the SQL standard, a base table is a table stored in the database catalog, as opposed to a view. The user defined name chosen for such a table is represented in the grammar by a nonterminal like base-table-identifier, which is defined in terms of user-defined-name. Another nonterminal, base-table-name, may then be defined as base-table-identifier with some additional context or qualifications. For boolean expressions, the grammar uses terms such as boolean-primary, which can be a comparison-predicate or other logical constructs. The productions shown in the options match this style and terminology, indicating that each one is a valid part of the SQL grammar rather than an invented phrase.

Step-by-Step Solution:
Step 1: Examine option A: base-table-identifier ::= user-defined-name. This states that a base table identifier is formed from a user defined name, which is consistent with SQL terminology for naming tables. Step 2: Examine option B: base-table-name ::= base-table-identifier. This production indicates that a base table name is built from the base-table-identifier, again matching how grammar definitions usually layer abstractions. Step 3: Examine option C: boolean-primary ::= comparison-predicate. This says that one form of a basic boolean expression is a comparison predicate, which aligns with SQL where comparisons such as column1 = column2 are boolean expressions. Step 4: Recognise that each production fits naturally into a SQL grammar: tables are named through identifiers, and boolean expressions can be comparison predicates. Step 5: Conclude that all three productions are legitimate grammar elements, making All of the above the correct answer.

Verification / Alternative check:
If you have seen simplified versions of the SQL standard grammar in textbooks or documentation, they frequently use nonterminals such as table-name, base-table-name, correlation-name, and boolean-primary. These grammar fragments define how SELECT, INSERT, and other statements are built. The style of the productions in the question matches these references. For example, boolean-primary often includes comparison-predicate as one of its alternatives, and base-table-name is typically associated with user defined table names. This consistency provides an alternative confirmation that the listed productions are indeed valid grammar elements.

Why Other Options Are Wrong:
Option base-table-identifier ::= user-defined-name: On its own, this is correct and forms part of SQL grammar, so it is not the sole correct choice when all options are correct. Option base-table-name ::= base-table-identifier: This is also a valid grammar production, but it is not the single best answer when considered alongside the others. Option boolean-primary ::= comparison-predicate: Likewise, this is a valid production but only part of the complete set of correct statements.

Common Pitfalls:
A typical mistake is to treat these productions as if they were complete SQL statements, which they are not. They are building blocks of a formal grammar. Another pitfall is to assume that unfamiliar names such as boolean-primary must be incorrect simply because they are not commonly used in everyday SQL conversation. In reality, the SQL standard uses many such internal names to describe parts of SQL expressions. Recognising the pattern of nonterminal ::= expansion helps you interpret these productions correctly.

Final Answer:
All the listed productions represent valid SQL grammar elements, so the correct choice is All of the above.