Database and SQL

ORDER BY can be used in view creation in most databases (Oracle, PostgreSQL, etc.) to specify the default presentation order when querying the view, though some databases like SQL Server restrict it.

Oracle imposes a 1000-column limit on views (and tables). Options 999 and 1001 are wrong, and the limit applies to both tables and views.

CREATE OR REPLACE VIEW is the simplest way to modify a view definition - it preserves permissions and dependencies. Dropping and recreating loses permissions and requires re-granting. ALTER VIEW doesn't exist for redefining views in most databases. UPDATE syntax is for data, not DDL.

In NPS (database systems), ALTER DATABASE is a DDL operation that typically requires exclusive access to the database. Most database systems lock the database or prevent concurrent DML operations during structural changes to maintain data integrity and prevent corruption.

When a subquery returns multiple rows, you must use set-based operators: IN checks membership in the result set, ALL compares against every value (e.g., salary > ALL means greater than the maximum), and ANY compares against any value (e.g., salary = ANY means equal to at least one, equivalent to IN). Standalone comparison operators like = or <> cannot directly handle multiple-row results.

SQL is a query language for accessing and manipulating data in Oracle databases and other RDBMS. The name SQL itself is the standard, complete name used in practice - it's not typically abbreviated further in technical documentation. In contrast, iSQL*Plus is a client tool/interface for executing SQL, not a language itself.

A SELECT statement returns a result set but does not create tables by itself - creating a table requires CREATE TABLE AS SELECT (CTAS) or SELECT INTO, which are DDL statements, not pure SELECT. Options B, C, and D are all capabilities of SELECT: specifying columns in the SELECT list, filtering rows with WHERE, and combining tables with JOIN.

Subqueries can be placed in the FROM clause (inline views), the HAVING clause of a SELECT statement, and the WHERE clause of UPDATE/DELETE/SELECT statements. ALTER is a DDL command and cannot contain subqueries in a SET clause.

In SQL, the DISTINCT keyword must appear immediately after the SELECT keyword and before the column list. This syntax is mandatory - DISTINCT cannot appear elsewhere in the SELECT clause. The keyword is part of the SELECT clause syntax, not a separate clause.

Option A correctly uses concatenation with || operator to combine columns and strings. Option C correctly concatenates string literals (quoted strings) - the column name 'ename' in quotes is a literal string, not a column reference, but this is valid SQL syntax. Options B and D have syntax errors.

Filters restrict result sets by applying conditions that narrow the data returned. Option B ('Filter occurrences') is vague and not a standard database concept. Option C is incorrect because while filters can reduce data volume, their primary purpose is data restriction, not performance enhancement - that's a side effect, not the function itself.

CREATE TABLE is a system privilege that allows a user to create tables in their schema. SELECT, EXECUTE (when on procedures), DELETE, and ALTER TABLE are object privileges that must be granted on specific database objects. System privileges are schema-wide authorities, while object privileges operate on named objects.

SQL provides built-in functions across multiple categories: character functions (SUBSTR, CONCAT, etc.), numeric functions (ABS, ROUND, etc.), date functions (SYSDATE, ADD_MONTHS, etc.), and conversion functions (TO_CHAR, TO_DATE, CAST, etc.). Option B correctly identifies character and numeric functions. Option E correctly identifies date and conversion functions. Option A is partially correct but incomplete. Options C, D, and F contain incorrect or non-standard category names.