How Can I Correctly Use Array Interfaces for Bulk Inserts with GORM\'s `tx.Exec()`?

Using Array Interface for GORM Bulk Inserts

Inserting multiple records into a database can often require constructing complex SQL queries. GORM simplifies this process, but it's important to understand how to correctly pass multiple values using an array interface.

Consider the following code:

vals := append(vals, "XX1", "Jakarta")
vals = append(vals, "XX2", "Bandung")

tx.Exec(sqlStr, vals)

This code would result in the following error:

Error 1136: Column count doesn't match value count at row 1

This is because the query expects four values (code, name, code, name), but the array interface vals is passed as a single argument instead of individual elements.

To fix this, we need to use the "..." operator to "unpack" the array interface and pass each element individually:

tx.Exec(sqlStr, vals...)

The signature of tx.Exec() is:

func (tx *Tx) Exec(query string, args ...interface{}) (Result, error)

So, we need to pass vals as vals.... Here's the corrected code:

res, err := tx.Exec(sqlStr, vals...)

Now, the query will be executed correctly, generating the desired SQL statement:

INSERT INTO city(code, name) VALUES ('XX1', 'Jakarta'),('XX2', 'Bandung')

Remember to check the returned error (err) after executing the query.

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