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SQL Server Tacklebox- P45: This book, as with almost all books, started out as an idea. I wanted to accumulate together those scripts and tools that I have built over the years so that DBAs could sort through them and perhaps adapt them for their own circumstances. | 8 Finding data corruption select from one n Results Messages NEOID NEOTEXT 542 542 BCDEFGHIJKLMNOPQR 543 543 ABCDEFGHIJKLMNOPQRSTUWX 544 544 XrZ 545 545 YZ 546 546 NOPQRSTUWXiZ 547 547 STUWX 548 548 HIJKLMN 548 548 DEFGHIJKLMNOPQR 550 550 RSTUWXrZ 551 551 CDEFGHUKLMNOPQR 552 552 DEFGHIJKLMNOPQRSTUWX 553 622 Z 554 623 IJKLMNOPQRSTUWXrZ 555 624 ABCDEFGHIJKLMNOP 556 625 EFGHIJKLMNOPQRSTUV 557 626 EFGHIJKLMNOPQRSTUWWZ 558 627 BCDEFGHIJKLMNOPQ 558 628 UWXrZ 560 628 RSTUWXrZ 561 630 MNOPQRSTUWXrZ 562 631 KLMNOPQRSTUWXrZ 563 632 YZ 564 633 OPQRSTUWXiZ 565 634 KLMNOPQRSTUWXrZ 566 635 WXrZ 567 636 W 568 637 BCDEFGHIJKL 568 638 LMNOPQRSTUWXrZ 570 638 MNOPQRSTUWXrZ 571 640 GHIJKLMNOPQRS 572 641 NOPQRSTUWXiZ 573 642 RSTUWXrZ 574 643 YZ 575 644 NOPQRSTUWXiZ Figure 8.11 Missing data after DBCC CHECKDB Repair_Allow_Data_Loss. These rows should be easily recovered if you have a good backup. You have a good backup right Right Assuming you do then you are faced with the task of restoring from backup to another database like NEO2 and syncing the two tables for the missing rows. Syncing the two tables can be accomplished with a simple insert into statement like that shown in Listing 8.4. 220 8 Finding data corruption INSERT INTO NEO.ONE NEOID NEOTEXT SELECT NEOID NEOTEXT FROM NEO2.ONE WHERE NEOID NOT IN SELECT NEOID FROM NEO.ONE Listing 8.4 Syncing two tables to recover lost data rows. In this controlled example the fix is fairly simple. Other scenarios with much higher levels of corruption may require you to turn to other measures to get the data back after repairing with data loss. These means will almost always involve a restore of the database from backup which is why I impress again the importance of a solid verified and well documented database backup policy. Corruption on non-clustered indexes I noted earlier that corruption of a non-clustered index is much easier to deal with than corruption of an actual data page as these indexes are just redundancies of the actual data and .
