Skip to main content

Using the Query

Building queries

The Query object is an interface that has a single method:

type Query interface {
// start is the index of the args, usually 1.
// it is present to allow re-indexing in cases of a subquery
// The method returns the value of any args placed
// An `io.Writer` is used for efficiency when building the query.
WriteQuery(w io.Writer, start int) (args []any, err error)

The WriteQuery method is useful when we want to write to an exisiting io.Writer. However we often just want the query string and arguments. So the Query objects have the following methods:

  • Build() (query string, args []any, err error)
  • BuildN(start int) (query string, args []any, err error)
  • MustBuild() (query string, args []any) // panics on error
  • MustBuildN(start int) (query string, args []any) // panics on error
queryString, args, err := psql.Select(...).Build()

Since the query is built from scratch every time the WriteQuery() method is called, it can be useful to initialize the query one time and reuse where necessary.

For that, the MustBuild() function can be used. This panics on error.

myquery, myargs := psql.Insert(...).MustBuild()

Executing queries

The returned query and args can then be passed to your querier (e.g. *sql.DB or *sql.Tx) to execute

ctx := context.Background()

// Build the query
myquery, myargs := psql.Insert(...).MustBuild()

// Execute the query
err := db.ExecContext(ctx, myquery, myargs...)

In addition to these, Bob also has a sql executor which can build and run queries in a single step.