How Can I Query Data With Unknown Column Types in Go\'s SQL Package?

Exploring Ad Hoc Queries in Go's SQL Package

While the documentation suggests that querying data in Go using the SQL package requires knowing column count and types at compile-time, this is not strictly true. The sql.Rows type offers a solution for flexible and ad hoc SQL queries.

Dynamic Column Metadata Retrieval

The Columns method in sql.Rows provides a list of the result column names. This allows you to dynamically determine the number of columns returned by an arbitrary query.

Scanning Unknown Data Types

The Scan method supports scanning values of unknown types into either a raw byte slice (*[]byte) or an interface{} value. This enables you to retrieve column data without pre-defining its type.

Working with Ad Hoc Queries

Combining these techniques, you can execute ad hoc queries and retrieve data into a slice of interface{} values:

<code class="go">columnNames, err := rows.Columns()
if err != nil {
    // Handle error
}
columns := make([]interface{}, len(columnNames))
columnPointers := make([]interface{}, len(columnNames))
for i := 0; i < len(columnNames); i++ {
    columnPointers[i] = &columns[i]
}
if err := rows.Scan(columnPointers...); err != nil {
    // Handle error
}</code>

After this, the columns slice will contain the decoded values for all columns in the result row. By leveraging the Columns and Scan methods, you can effectively handle ad hoc queries in Go's SQL package.

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