How to declare a SQL row, if else statement not declared problem - go

Question

I have a code like this below.
var sql string
if pnt.Type == "newType" {
sql = `select code, count(*) count from (
select code
from code_table
where start >= ? and end <= ?
union
select code
from code_table
where start >= ? and end <= ?
) a group by code`
rows, err := pnt.readConn("testdb").Query(sql, start, end, start, end)
} else {
sql = `select code, count(*) count from code_table where start >= ? and end <= ?` group by code
rows, err := pnt.readConn("testdb").Query(sql, start, end)
}
if err == nil {
defer rows.Close()
for rows.Next() {
var code, count int
rows.Scan(&code, &count)
}
} else {
log.Println(err)
}
This will give me an error something like this "Variable not declared for rows, err"...
I've tried declaring "var err error" and within the if else statement, I use = instead of :=
something like this
var err error
rows, err = pnt.switchConn("base", "read").Query(sql, start, end)
However, I still can't declare the rows cuz I will have different kind of errors for that. I tried declaring it as string but no luck.
This is my first time using golang and the if else thing is giving me a hard time, why can't I just use := inside if else statement. As you can see, I can't use rows, err := outside the if else statement, cuz both have different numbers of parameters.

Answer 1

You are facing issues because of the scope of the variable.
In Golang, := creates a new variable inside a scope.
rows, err := pnt.ReadConn("testdb").Query(sql, start, end, start, end)
Creates a new rows and err variables in the if block which won't be accessible outside the if block.
Shorthand declarations in Go
The fix,
var sql string
var err error
var rows *sql.Rows
if pnt.Type == "newType" {
sql = `select code, count(*) count from (
select code
from code_table
where start >= ? and end <= ?
union
select code
from code_table
where start >= ? and end <= ?
) a group by code`
rows, err = pnt.ReadConn("testdb").Query(sql, start, end, start, end)
} else {
sql = `select code, count(*) count from code_table where start >= ? and end <= ?` group by code
rows, err = pnt.ReadConn("testdb").Query(sql, start, end)
}
if err == nil {
defer rows.Close()
for rows.Next() {
var code, count int
rows.Scan(&code, &count)
}
} else {
log.Println(err)
}

Answer 2

In golang ":=" mean you declare a variable and assign them a this value GO will automatically detect his type so :
Exemples
variable := 15
It’s the same
var variable int = 15
So when you do this rows, err := pnt.switchConn("base", "read").Query(sql, start, end, start, end)
} else {
sql =select code, count(*) count from code_table where start >= ? and end <= ?group by code
rows, err := pnt.switchConn("base", "read").Query(sql, start, end)
}
You declare the same variable rows and err twice