英文:
query is returning "expected 0 arguments, got 1"
问题
我正在尝试查询一个我知道其中有数据的数据库，直接在pgadmin中查询时是有结果的。但是，当我使用以下代码进行查询时，却没有返回结果：
const DATABATE_URL = "postgres://postgres:pw@localhost:5432/postgresdb"
conn, err := pgx.Connect(context.Background(), DATABATE_URL)
defer conn.Close(context.Background())
if err != nil {
fmt.Printf("Connection failed: %v\n", err)
os.Exit(-1)
}
stmt := "SELECT * FROM nodes"
rows, err := conn.Query(context.Background(), stmt, nil)
if err != nil {
fmt.Fprintf(os.Stderr, "QueryRow failed: %v\n", err) // 在这里报错 "expected 0 arguments, got 1"
os.Exit(1)
}
for rows.Next() {
var results string
err = rows.Scan(&results)
if err != nil {
fmt.Fprintf(os.Stderr, "QueryRow failed: %v\n %n", err)
os.Exit(1)
}
fmt.Println(results)
}
当我通过 Goland 和 pgadmin 直接连接到数据库并使用相同的语句进行查询时，我可以看到所有的数据。我在这里漏掉了什么？
英文:
I am trying to query a database that I know has data in it from directly querying within pgadmin. When I query using the following code it returns no results:
const DATABATE_URL = "postgres://postgres:pw@localhost:5432/postgresdb"
conn, err := pgx.Connect(context.Background(), DATABATE_URL)
defer conn.Close(context.Background())
if err != nil {
fmt.Printf("Connection failed: %v\n", err)
os.Exit(-1)
}
stmt := "SELECT * FROM nodes"
rows, err := conn.Query(context.Background(), stmt, nil)
if err != nil {
fmt.Fprintf(os.Stderr, "QueryRow failed: %v\n", err) //error outs here "expected 0 arguments, got 1"
os.Exit(1)
}
for rows.Next() {
var results string
err = rows.Scan(&results)
if err != nil {
fmt.Fprintf(os.Stderr, "QueryRow failed: %v\n %n", err)
os.Exit(1)
}
fmt.Println(results)
}
When I directly connect to the database through goland and pgadmin and query with the same statement I can see all the data. What am I missing here?
答案1
得分: 1
pgx的Conn.Query方法接受一个上下文、语句和参数：
func (c *Conn) Query(ctx context.Context, sql string, args ...interface{}) (Rows, error)
你传递给它一个上下文、语句和nil：
rows, err := conn.Query(context.Background(), stmt, nil)
所以nil被当作参数处理，但是你的SQL语句中没有包含任何参数占位符（例如SELECT * FROM nodes where id=$1），因此出现了错误。要修复这个问题，请运行：
rows, err := conn.Query(context.Background(), stmt)
然而，修改你的SQL语句以指定你想要的列也是值得的（例如SELECT nodename FROM nodes）。
注意：当提出这样的问题时，请将错误包含在问题正文中，而不仅仅作为代码的注释（这样很容易被忽略）。
英文:
The pgx Conn.Query accepts a context, statement and arguments:
func (c *Conn) Query(ctx context.Context, sql string, args ...interface{}) (Rows, error)
You are passing it a context, statement and nil:
rows, err := conn.Query(context.Background(), stmt, nil)
So the nil is treated as an argument but your SQL statement does not contain any argument placeholders (e.g. SELECT * FROM nodes where id=$1) hence the error. To fix this run:
rows, err := conn.Query(context.Background(), stmt)
However it would also be worth editing your sql to specify the column you want (e.g. SELECT nodename FROM nodes).
Note: When raising a question like this please include the error in the question body rather than just as a comment in the code (which is easy to miss).
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