UDAs (User-Defined Aggregates), 430
UDFs (user-defined functions)
extending check constraints with, 200–202
scalar UDFs in query performance, 294–296
SQL Server 2005, 61
table-valued UDFs in query performance, 296
used with subqueries, 202–204
UDTs (User-Defined Types), 430
UMS (User Mode Scheduler), 406
SQLOS compared with, 417
SQLOS replaces, 408
Unicode data, 335
UNION
combining results of two or more SELECT statements, 57
query execution order and, 286
using with linked servers, 352
unique key constraints, 195
UNIX clients, 19
UNPIVOT operator, SELECT statements, 54
UNSAFE assemblies, 428
update locks (U-locks), 236
UPDATE statements
OUTPUT keyword, 261, 266
query hints and, 71
steps in processing, 457
subqueries, 50
within snapshot transaction, 248
updates, concurrency problems and, 246
UPDLOCK, locking hints, 261, 265
USE, query hints, 71
user control-level output caching, 100–101
compared with page-level, 100
when to use, 101
User DSN, 8
user IDs, 9
User-Defined Aggregates (UDAs), 430
user-defined data types (UDTs), 335, 430
user-defined functions. See UDFs (user-defined functions)
user-defined messages
error handling, 225
localizing for error handling, 226
User Mode Scheduler (UMS), 406
SQLOS compared with, 417
SQLOS replaces, 408