What approaches exist for dynamically constructing SQL SELECT queries with the ability to change conditions and parameters?

For dynamically constructing a SELECT SQL query in Go, there are several approaches:

1. String concatenation — the simplest but unsafe method, prone to SQL injection.

2. Using parameterized queries with the database/sql package and passing arguments via ? or $1.

3. Query builders — libraries that allow programmatic query formation with conditions, sorting, etc.

Example using the Squirrel library:

import (
    "github.com/Masterminds/squirrel"
    "database/sql"
    _ "github.com/lib/pq"
)

func buildQuery(age int, active bool) (string, []interface{}, error) {
    qb := squirrel.Select("id", "name").From("users")

    if age > 0 {
        qb = qb.Where(squirrel.Gt{"age": age})
    }
    if active {
        qb = qb.Where(squirrel.Eq{"active": true})
    }

    return qb.ToSql()
}

func main() {
    db, _ := sql.Open("postgres", "connection_string")
    query, args, _ := buildQuery(30, true)
    rows, _ := db.Query(query, args...)
    defer rows.Close()
    // process results
}

This approach allows dynamic addition of conditions and parameters, avoiding errors and SQL injection.

You can also use ORM or custom query construction wrappers.