Bagaimana saya bisa melihat berapa banyak baris yang 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'
GO

0,

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

1,

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

2,

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

3,

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

4,

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

5, 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'
GO

6 mengatur ulang nilai @@ROWCOUNT menjadi ________4______8

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