Database and SQL

IGNORE DUPLICATE ROWS is ignored when a table has unique indexes because the unique index constraint still enforces uniqueness at the database level. The option only applies to tables without unique indexes.

Teradata MLOAD supports the DROP DDL statement, allowing users to drop tables as part of the MLOAD script. However, MLOAD does not support CREATE, ALTER, or RENAME DDL statements - these must be executed separately outside of MLOAD. MLOAD is optimized for high-volume data loading with limited DDL support, focusing on DELETE and INSERT operations along with DROP for target table management.

In SQL join conditions, table names are NOT mandatory when column names are unambiguous (unique across joined tables). However, it's best practice to qualify column names to avoid ambiguity and improve code clarity.

An outer join returns records from one table even when there's no matching record in the other table. This is useful for finding unmatched records (like customers without orders) or maintaining all records from a primary table.

The (+) symbol is the Oracle-specific outer join operator, traditionally used before ANSI standard JOIN syntax was adopted. It's placed on the side of the join condition that may be missing (NULL).

A self-join joins a table to itself, treating it as if it were two separate tables. This is useful for comparing rows within the same table, such as finding employee-manager relationships in an employees table.

To join N tables together, you need N-1 join conditions. For 10 tables, you need 9 join statements. This follows the principle that each new table requires one additional join to link it to the existing structure.

SQL allows ordering by column aliases defined in the SELECT list, because the alias is resolved after the SELECT clause but before ORDER BY is processed. Hence sorting by an alias is possible, making the claim that it isn’t possible false.

SQL functions are categorized into single-row functions (operate on one row at a time, like UPPER, SUBSTR) and multiple-row functions (operate on groups of rows, like SUM, COUNT, AVG). This classification determines how they're used in queries.

Single‑row functions, such as UPPER or SYSDATE, operate on each row individually and return exactly one value per row. They cannot produce multiple results from a single input row; that behavior belongs to set‑returning functions, making the statement false.

The LIKE operator is standard SQL terminology for performing wildcard searches using pattern matching characters. It is used in the WHERE clause.

An equi-join is a join based on equality between columns, typically joining on the same column name from different tables. Option B shows Table1.column1 = Table2.column1, which represents an equi-join condition where the same column from both tables is being compared for equality.

A non-equijoin is a join condition that evaluates relationships other than equality, such as using operators like BETWEEN, greater than, or less than. It matches values within specified ranges rather than exact matches.