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ix
Using cursors on SELECT statements in procedures ........... 253
Errors and warnings in procedures .............................................. 255
Default error handling in procedures ..................................... 256
Error handling with ON EXCEPTION RESUME.................... 258
Default handling of warnings in procedures .......................... 260
Using exception handlers in procedures ............................... 261
Nested compound statements and exception handlers ........ 263
Using the EXECUTE IMMEDIATE statement in procedures ....... 264
Transactions and savepoints in procedures................................. 265
Some tips for writing procedures.................................................. 265
Check if you need to change the command delimiter ........... 265
Remember to delimit statements within your procedure ....... 266
Use fully-qualified names for tables in procedures................ 266
Specifying dates and times in procedures............................. 266
Verifying procedure input arguments .................................... 267
Statements allowed in batches .................................................... 267
Using SELECT statements in batches .................................. 268
Calling external libraries from procedures.................................... 268
Creating procedures and functions with external calls .......... 269
External function declarations ............................................... 270
How parameters are passed to the external function............ 271
Special considerations when passing character types.......... 272
CHAPTER 7 Ensuring Data Integrity .............................................................. 273
Data integrity overview................................................................. 273
How data can become invalid ............................................... 273
Integrity constraints belong in the database.......................... 274
How database contents get changed.................................... 275
Data integrity tools................................................................. 275
SQL statements for implementing integrity constraints ......... 276
Using table and column constraints ............................................. 277
Using UNIQUE constraints on columns or tables.................. 277
Using IQ UNIQUE constraint on columns ............................. 278
Using CHECK conditions on columns................................... 278
Column CHECK conditions from user-defined data types .... 279
Working with column constraints in Sybase Central ............. 280
Using CHECK conditions on tables....................................... 280
Modifying and deleting CHECK conditions............................ 280
Declaring entity and referential integrity....................................... 281
Enforcing entity integrity........................................................ 282
If a client application breaches entity integrity....................... 282
Primary keys enforce entity integrity ..................................... 283
Declaring referential integrity................................................. 283
How you define foreign keys ................................................. 284