compiler: Add tests for COALESCE behavior (#1112)

Author: kyleconroy

internal/endtoend/testdata/coalesce/postgresql/pgx/go/models.go

@@ -1,9 +1,30 @@
-CREATE TABLE foo (bar text, bat text not null);
+CREATE TABLE foo (
+    bar text,
+    bat text not null,
+    baz bigint,
+    qux bigint not null
+);
 
--- name: Coalesce :many
+-- name: CoalesceString :many
 SELECT coalesce(bar, '') as login
 FROM foo;
 
--- name: CoalesceColumns :many
+-- name: CoalesceNumeric :many
+SELECT coalesce(baz, 0) as login
+FROM foo;
+
+-- name: CoalesceStringColumns :many
 SELECT bar, bat, coalesce(bar, bat)
 FROM foo;
+
+-- name: CoalesceNumericColumns :many
+SELECT baz, qux, coalesce(baz, qux)
+FROM foo;
+
+-- name: CoalesceStringNull :many
+SELECT bar, coalesce(bar)
+FROM foo;
+
+-- name: CoalesceNumericNull :many
+SELECT baz, coalesce(baz)
+FROM foo;