The execution plan is the primary diagnostic tool for query performance. It reveals how the database engine executes the query, showing table scan operations, join methods used, and potential index usage. This information is essential before taking any corrective action, such as creating targeted indexes, to avoid unnecessary changes.

The principle of least privilege mandates that users should have only the permissions necessary for their current tasks. An unused account with excessive privileges (like DBA) is a significant security risk. The immediate and correct action is to revoke the unnecessary high-level privilege. Simply changing the password or creating a new account does not remove the excessive access from the original account.

This describes a many-to-many relationship: one order has many products, and one product can be in many orders. The correct, normalized design uses three tables: Orders (OrderID), Products (ProductID), and a junction/linking table (e.g., Order_Details) with foreign keys to both parent tables. This structure efficiently supports both query requirements without data redundancy or arbitrary limits.

In FULL recovery mode, the combination of a full backup and the subsequent chain of transaction log backups allows for point-in-time recovery (PITR). To recover to the moment just before the accidental delete (4:14 PM), you must restore the last full backup WITH NORECOVERY and then apply every transaction log backup in sequence, recovering the last log to the specific point in time.

For a composite index, the column order is critical. The database can efficiently use the index for searching only if the query includes conditions on a leading prefix of the index columns. A query filtering only on `Status` (the second column) skips the first column (`Region`). The database may choose to do a slower full index scan instead of a fast seek, or it may ignore the index entirely.

Connection pool exhaustion is most commonly caused by connection leaks in the application layer. If the application fails to close connections (e.g., due to unhandled exceptions, missing finally blocks), those connections remain open and eventually consume all available connections in the pool, leading to timeouts for new requests. This should be investigated before infrastructure issues.

Document databases (e.g., MongoDB, Couchbase) are explicitly designed to store, retrieve, and manage semi-structured data as documents (like JSON, BSON). They are ideal for use cases like user profiles where each record can have a different set of fields, providing the required flexibility and efficient querying within the document structure.

CHECK constraints are the standard, declarative way to enforce domain integrity by restricting the values that can be placed in a column. They can validate that a value is positive (Salary > 0) or matches a pattern (Email LIKE ‘%@%’). This enforcement happens at the database level, ensuring data quality regardless of the application used to insert it.

Tables with sequential keys (like identity columns or dates) are prone to page splits at the end of the index, leading to logical fragmentation. Over time, this fragmentation causes inefficient range scans. Rebuilding or reorganizing the index defragments the physical storage of the index pages, making sequential I/O operations for range scans much more efficient.

The execution plan is the primary diagnostic tool for query performance. It reveals how the database engine executes the query, showing table scan operations, join methods used, and potential index usage. This information is essential before taking any corrective action, such as creating targeted indexes, to avoid unnecessary changes.0