SuperDB

Inputs

Input data is processed by queries through expressions that contain input-data references.

In pipe scoping, input data is always referenced as the special value this.

In relational scoping, input data is referenced by specifying the columns of one or more tables. See the SQL section for details on how columns are bound to identifiers, how table references are resolved, and how this behaves in a SQL expression.

The type of this may be any type. When this is a record, references to fields of the record may be referenced by an identifier that names the field of the implied this value, e.g., x means this.x.

For expressions that appear in a SQL operator, input is presumed to be in the form of records and is referenced using relational scoping. Here, identifiers refer to table aliases and/or column names and are bound to the available inputs based on SQL semantics. When the input schema is known, these references are statically checked and compile-time errors are raised when invalid tables or columns are referenced.

In a SQL operator, if the input is not a record (i.e., not relational), then the input data can still be referred to as the value this and placed into an output relation using SELECT. When referring to non-relational with *, there are no input columns and thus the select value is empty, i.e., the value {}.

When non-record data is referenced in a SQL operator and the input schema is dynamic and unknown, runtime errors like error("missing") will generally arise and be present in the output data.

Examples

A simple reference to this

# spq
values this
# input
1
true
"foo"
# expected output
1
true
"foo"

Referencing a field of this

# spq
values this.x
# input
{x:1,y:4}
{x:2,y:5}
{x:3,y:6}
# expected output
1
2
3

Referencing an implied field of this

# spq
values x
# input
{x:1,y:4}
{x:2,y:5}
{x:3,y:6}
# expected output
1
2
3

Selecting a column of an input table in a SQL operator

# spq
SELECT x
# input
{x:1,y:4}
{x:2,y:5}
{x:3,y:6}
# expected output
{x:1}
{x:2}
{x:3}

Selecting a column of an named input table

# spq
let input = (
  values
    {x:1,y:4},
    {x:2,y:5},
    {x:3,y:6}
)
SELECT x FROM input
# input

# expected output
{x:1}
{x:2}
{x:3}