Database and SQL

SQL is a declarative language, not procedural. In SQL, you specify what data you want (declarative), not how to retrieve it (procedural). The database engine determines the optimal execution plan. Procedural languages like C or Java require step-by-step instructions including loops and conditional logic.

Catch_#22 is a valid column name in SQL. While it looks unusual, SQL allows column names to contain underscores and numbers. The rules vary by database: some require quotes for special characters, but alphanumeric names with underscores are generally acceptable. The # character might require quoting in some databases, but the name itself is syntactically possible.

In SQL query execution, WHERE clause filters individual rows BEFORE grouping, while HAVING clause filters groups AFTER aggregation. The logical order is: FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY. WHERE cannot use aggregate functions, but HAVING can. This is why WHERE conditions are applied first to reduce the row set before grouping.

Pre-query trigger fires once before the query executes. Post-query trigger fires once per record fetched, so for 10 records it fires 10 times. This makes option B (1,10) correct.

The KEY-OTHERS trigger in Oracle Forms defines the action to be taken when a user presses a function key that does not have its own specific key trigger defined, preventing default behavior or providing a fallback.

PRE-UPDATE triggers have restricted built-in usage. DOWN is for navigation, COMMIT_FORM would cause recursion, and GO_ITEM is restricted in this context. These built-ins cannot be used in PRE-UPDATE triggers.

When Validation Unit is Form, item-level validation (and thus PRE-TEXT-ITEM triggers) is bypassed. Validation occurs only at form level (e.g., on commit), so PRE-TEXT-ITEM never fires.

When creating a table in a relational database, you do not need to specify its physical size, as storage is allocated dynamically. Tables can be created while users are active, and their structures can be modified online.

In Oracle SQL, the ALTER TABLE...MODIFY command can convert legacy LONG and LONG RAW data types to modern LOB (Large OBject) types like CLOB and BLOB. This helps migrate older database schemas to use more flexible large object types.

The ALTER TABLE...ENABLE CONSTRAINT command re-enables a previously disabled constraint. This will successfully enable the PRIMARY KEY constraint inventory_id_pk and validate existing data, achieving the desired result.

CONCAT concatenates strings, RPAD pads strings with specified characters to the right, and INSTR finds the position of a substring within a string. All three are character manipulation functions in SQL that work on text data.

PRIMARY KEY and UNIQUE constraints automatically create unique indexes to enforce uniqueness. NOT NULL explicitly prevents null values. UNIQUE constraints do permit null values (one per column in Oracle, multiple in standard SQL - though Oracle treats NULLs as not equal to each other), and FOREIGN KEY constraints create indexes for referential integrity checking but not unique indexes.

MERGE combines insert and update operations in a single statement to synchronize tables. It inserts new rows when matches aren't found and updates existing rows when matches exist. MERGE does not replace entire table contents - it performs targeted operations based on match conditions between source and target.

Oracle table names must start with a letter, can contain letters, digits, and underscores, and cannot be a reserved word. Option A (EMP9$#) is valid because $ and # are allowed characters. Options B (*), C (PACKAGE is reserved), and D (starts with digit 1) are invalid.