Bagaimana baris cek terpengaruh di mysql?

Di SQL Server, Anda dapat menggunakan fungsi sistem @@ROWCOUNT untuk mengembalikan jumlah baris yang terpengaruh oleh pernyataan T-SQL terakhir

Misalnya, jika kueri mengembalikan 4 baris, @@ROWCOUNT akan mengembalikan 4

Contoh 1 – Memilih Data

Berikut adalah contoh dasar untuk menunjukkan cara kerjanya

SELECT * FROM Dogs; SELECT @@ROWCOUNT;

Hasil

+---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)_

Dalam hal ini, pernyataan +---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)_0 saya mengembalikan 3 baris, sehingga @@ROWCOUNT mengembalikan 3

Contoh 2 – Memperbarui Data

Berikut adalah contoh penggunaan @@ROWCOUNT dengan pernyataan +---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)3 untuk menguji apakah ada baris yang diperbarui atau tidak

UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO_

Hasil

(0 rows affected) A dog outside the system cannot be a good dog

Dalam hal ini, tidak ada baris yang diperbarui karena DogId tidak ada di tabel. Kami dapat menggunakan @@ROWCOUNT dengan pernyataan +---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)5 untuk mengembalikan pesan yang sesuai kepada pengguna

Ini dia lagi, tapi kali ini anjingnya memang ada

UPDATE Dogs SET GoodDog = 1 WHERE DogId = 1 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO

Hasil

(1 row affected) Your dog will be rewarded accordingly_

Kumpulan Data yang Sangat Besar?

Jika menurut Anda jumlah baris yang dipengaruhi oleh pernyataan akan lebih dari 2 miliar, gunakan +---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)6 sebagai gantinya

Anda dapat menggunakannya dengan cara yang sama seperti @@ROWCOUNT digunakan

UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF ROWCOUNT_BIG() > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO

Hasil

(0 rows affected) A dog outside the system cannot be a good dog

Ketika @@ROWCOUNT adalah Reset

Pernyataan seperti +---------+-----------+-----------+ | DogId   | DogName   | GoodDog   | |---------+-----------+-----------| | 1       | Fetch     | 0         | | 2       | Fluffy    | 0         | | 3       | Wag       | 0         | +---------+-----------+-----------+ (3 rows affected) +--------------------+ | (No column name)   | |--------------------| | 3                  | +--------------------+ (1 row affected)9, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO0, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO1, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO2, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO3, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO4, UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO5, atau UPDATE Dogs SET GoodDog = 1 WHERE DogId = 4 IF @@ROWCOUNT > 0 PRINT 'Your dog will be rewarded accordingly'; ELSE PRINT 'A dog outside the system cannot be a good dog' GO6 mengatur ulang nilai @@ROWCOUNT menjadi ________4______8

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