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From SQL types to Go types: DuckDB and MySQL

Every file of the DuckDB and MySQL versions side by side, with the lines that differ marked.

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Configuration

sgl.yamldiffers
DuckDB
MySQL
1version: 1
1version: 1
2
2
3databases:
3databases:
4 - name: harbour
4 - name: landings
5 dialect: duckdb
5 dialect: mysql
6 migrations: db/migrations
6 migrations: db/migrations
7 queries: db/queries
7 queries: db/queries
8 go:
8 go:
9 package: store
9 package: store
10 out: internal/store
10 out: internal/store

Migrations

db/migrations/0001_landings.up.sqldiffers
DuckDB
MySQL
1CREATE SEQUENCE landing_ids;
2
3CREATE TABLE landings (
1CREATE TABLE landings (
4 id BIGINT PRIMARY KEY DEFAULT nextval('landing_ids'),
2 id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
5 species VARCHAR NOT NULL,
3 species VARCHAR(50) NOT NULL,
6 quay UTINYINT NOT NULL,
4 boxes SMALLINT NOT NULL,
7 boxes SMALLINT NOT NULL,
5 fish INT NOT NULL,
8 fish INTEGER NOT NULL,
6 weight_g BIGINT NOT NULL,
9 weight_g BIGINT NOT NULL,
7 length_cm DOUBLE NOT NULL,
10 length_cm DOUBLE NOT NULL,
8 on_ice BOOLEAN NOT NULL,
11 water_temp REAL NOT NULL,
9 landed_at DATETIME NOT NULL,
12 on_ice BOOLEAN NOT NULL,
10 tag VARBINARY(16) NOT NULL,
13 landed_at TIMESTAMP NOT NULL,
11 notes TEXT,
14 landed_on DATE NOT NULL,
12 berth TINYINT UNSIGNED NOT NULL,
15 catch_id UUID NOT NULL,
13 price_per_kg DECIMAL(6, 2) NOT NULL
16 auction_lot HUGEINT NOT NULL,
17 tag BLOB NOT NULL,
18 notes VARCHAR
19);
14);
db/migrations/0001_landings.down.sqldiffers
DuckDB
MySQL
1DROP TABLE landings;
1DROP TABLE landings;
2DROP SEQUENCE landing_ids;

Queries

RecordLandingdiffers
DuckDB · db/queries/landings.sql
MySQL · db/queries/landings.sql
1-- sgl.query(RecordLanding, one)
1-- sgl.query(RecordLanding, execresult)
2INSERT INTO landings (species, quay, boxes, fish, weight_g, length_cm, water_temp, on_ice, landed_at, landed_on, catch_id, auction_lot, tag, notes)
2-- ?11 as sgl.param(price_per_kg, type: text)
3VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
3INSERT INTO landings (species, boxes, fish, weight_g, length_cm, on_ice, landed_at, tag, notes, berth, price_per_kg)
4RETURNING id;
4VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
GetLandingdiffers
DuckDB · db/queries/landings.sql
MySQL · db/queries/landings.sql
1-- sgl.query(GetLanding, one)
1-- sgl.query(GetLanding, one)
2SELECT id, species, quay, boxes, fish, weight_g, length_cm, water_temp, on_ice, landed_at, landed_on, catch_id, auction_lot, tag, notes
2SELECT id, species, boxes, fish, weight_g, length_cm, on_ice, landed_at, tag, notes, berth, price_per_kg
3FROM landings
3FROM landings
4WHERE id = $1;
4WHERE id = ?;

What sgl generates

RecordLandingdiffers
DuckDB
MySQL
1func (queries *Queries) RecordLanding(ctx context.Context, params RecordLandingParams) (RecordLandingRow, error)
1func (queries *Queries) RecordLanding(ctx context.Context, params RecordLandingParams) (sql.Result, error)
2
2
3type RecordLandingParams struct {
3type RecordLandingParams struct {
4 Species string
4 Species string
5 Quay uint8
6 Boxes int16
5 Boxes int16
7 Fish int32
6 Fish int32
8 WeightG int64
7 WeightG int64
9 LengthCm float64
8 LengthCm float64
10 WaterTemp float32
11 OnIce bool
9 OnIce bool
12 LandedAt time.Time
10 LandedAt time.Time
13 LandedOn time.Time
14 CatchID uuid.UUID
15 AuctionLot *big.Int
16 Tag []byte
11 Tag []byte
17 Notes *string
12 Notes *string
18}
13 Berth uint8
19
14 PricePerKg string
20type RecordLandingRow struct {
21 ID int64 `json:"id"`
22}
15}
GetLandingdiffers
DuckDB
MySQL
1func (queries *Queries) GetLanding(ctx context.Context, id int64) (GetLandingRow, error)
1func (queries *Queries) GetLanding(ctx context.Context, id int64) (GetLandingRow, error)
2
2
3type GetLandingRow struct {
3type GetLandingRow struct {
4 ID int64 `json:"id"`
4 ID int64 `json:"id"`
5 Species string `json:"species"`
5 Species string `json:"species"`
6 Quay uint8 `json:"quay"`
6 Boxes int16 `json:"boxes"`
7 Boxes int16 `json:"boxes"`
7 Fish int32 `json:"fish"`
8 Fish int32 `json:"fish"`
8 WeightG int64 `json:"weight_g"`
9 WeightG int64 `json:"weight_g"`
9 LengthCm float64 `json:"length_cm"`
10 LengthCm float64 `json:"length_cm"`
10 OnIce bool `json:"on_ice"`
11 WaterTemp float32 `json:"water_temp"`
11 LandedAt time.Time `json:"landed_at"`
12 OnIce bool `json:"on_ice"`
12 Tag []byte `json:"tag"`
13 LandedAt time.Time `json:"landed_at"`
13 Notes *string `json:"notes"`
14 LandedOn time.Time `json:"landed_on"`
14 Berth uint8 `json:"berth"`
15 CatchID uuid.UUID `json:"catch_id"`
15 PricePerKg apd.Decimal `json:"price_per_kg"`
16 AuctionLot *big.Int `json:"auction_lot"`
17 Tag []byte `json:"tag"`
18 Notes *string `json:"notes"`
19}
16}

The program

example.godiffers
DuckDB
MySQL
1package main
1package main
2
2
3import (
3import (
4 "context"
4 "context"
5 "database/sql"
5 "database/sql"
6 "errors"
7 "fmt"
6 "fmt"
8 "io"
7 "io"
9 "math/big"
10 "time"
8 "time"
11
9
12 "github.com/google/uuid"
10 "seagull.sh/seagull/examples/mysql/005_type_mapping/internal/store"
13
14 "seagull.sh/seagull/examples/duckdb/005_type_mapping/internal/store"
15)
11)
16
12
17// run records a landing of fish and reads it back, printing the Go type sgl chose for
13// run records a landing of fish and reads it back, printing the Go type sgl chose for
18// each column. DuckDB declares every column's type exactly, and Seagull maps each one:
14// each column. Seagull maps the type each column declares in db/migrations: SMALLINT, INT
15// and BIGINT give int16, int32 and int64, and an UNSIGNED integer gives the unsigned Go
16// type of the same width, so TINYINT UNSIGNED is uint8. DOUBLE gives float64, BOOLEAN
17// (MySQL's TINYINT(1)) gives bool, DATETIME gives time.Time when the DSN sets
18// parseTime=true, and VARBINARY gives []byte.
19//
19//
20// - SMALLINT, INTEGER and BIGINT give int16, int32 and int64, and the unsigned UTINYINT
20// DECIMAL gives apd.Decimal from github.com/cockroachdb/apd/v3, which holds the exact
21// gives uint8;
21// value. The insert binds the price as text instead, through sgl.param(price_per_kg,
22// - DOUBLE gives float64, but REAL is DuckDB's 4-byte float, so it gives float32;
22// type: text), and MySQL converts "4.20" to DECIMAL(6, 2) without rounding.
23// - TIMESTAMP and DATE give time.Time, and UUID gives uuid.UUID from
24// github.com/google/uuid;
25// - HUGEINT is a 128-bit integer with no Go equivalent, so it gives *big.Int, the type
26// duckdb-go returns, even when the column is NOT NULL;
27// - BLOB gives []byte, and a nullable VARCHAR gives *string.
28//
23//
29// Takes database (*sql.DB) which is a migrated database.
24// Takes database (*sql.DB) which is a migrated database.
30// Takes output (io.Writer) which receives one line per column.
25// Takes output (io.Writer) which receives one line per column.
31//
26//
32// Returns error when a query fails.
27// Returns error when a query fails.
33func run(ctx context.Context, database *sql.DB, output io.Writer) error {
28func run(ctx context.Context, database *sql.DB, output io.Writer) error {
34 queries := store.New(database)
29 queries := store.New(database)
35
30
36 // The auction lot number has 20 digits, too many for int64 or uint64.
31 result, err := queries.RecordLanding(ctx, store.RecordLandingParams{
37 lot, ok := new(big.Int).SetString("20260501000000000001", 10)
38 if !ok {
39 return errors.New("parsing the auction lot number")
40 }
41 recorded, err := queries.RecordLanding(ctx, store.RecordLandingParams{
42 Species: "mackerel",
32 Species: "mackerel",
43 Quay: 3,
44 Boxes: 12,
33 Boxes: 12,
45 Fish: 480,
34 Fish: 480,
46 WeightG: 163_200,
35 WeightG: 163_200,
47 LengthCm: 31.5,
36 LengthCm: 31.5,
48 WaterTemp: 11.25,
49 OnIce: true,
37 OnIce: true,
50 LandedAt: time.Date(2026, time.May, 1, 5, 30, 0, 0, time.UTC),
38 LandedAt: time.Date(2026, time.May, 1, 5, 30, 0, 0, time.UTC),
51 LandedOn: time.Date(2026, time.May, 1, 0, 0, 0, 0, time.UTC),
52 CatchID: uuid.MustParse("6f1c2a5e-4d3b-4c2a-9e8f-1a2b3c4d5e6f"),
53 AuctionLot: lot,
54 Tag: []byte{0x04, 0xa2, 0x19, 0xf3},
39 Tag: []byte{0x04, 0xa2, 0x19, 0xf3},
55 Notes: new("landed at Newlyn"),
40 Notes: new("landed at Newlyn"),
41 Berth: 7,
42 PricePerKg: "4.20",
56 })
43 })
57 if err != nil {
44 if err != nil {
58 return fmt.Errorf("recording a landing: %w", err)
45 return fmt.Errorf("recording a landing: %w", err)
59 }
46 }
47 id, err := result.LastInsertId()
48 if err != nil {
49 return fmt.Errorf("reading the landing's id: %w", err)
50 }
60
51
61 landing, err := queries.GetLanding(ctx, recorded.ID)
52 landing, err := queries.GetLanding(ctx, id)
62 if err != nil {
53 if err != nil {
63 return fmt.Errorf("getting landing %d: %w", recorded.ID, err)
54 return fmt.Errorf("getting landing %d: %w", id, err)
64 }
55 }
65 fmt.Fprintf(output, "id %-10T %d\n", landing.ID, landing.ID)
56 fmt.Fprintf(output, "id %-12T %d\n", landing.ID, landing.ID)
66 fmt.Fprintf(output, "species %-10T %s\n", landing.Species, landing.Species)
57 fmt.Fprintf(output, "species %-12T %s\n", landing.Species, landing.Species)
67 fmt.Fprintf(output, "quay %-10T %d\n", landing.Quay, landing.Quay)
58 fmt.Fprintf(output, "boxes %-12T %d\n", landing.Boxes, landing.Boxes)
68 fmt.Fprintf(output, "boxes %-10T %d\n", landing.Boxes, landing.Boxes)
59 fmt.Fprintf(output, "fish %-12T %d\n", landing.Fish, landing.Fish)
69 fmt.Fprintf(output, "fish %-10T %d\n", landing.Fish, landing.Fish)
60 fmt.Fprintf(output, "weight_g %-12T %d\n", landing.WeightG, landing.WeightG)
70 fmt.Fprintf(output, "weight_g %-10T %d\n", landing.WeightG, landing.WeightG)
61 fmt.Fprintf(output, "length_cm %-12T %.1f\n", landing.LengthCm, landing.LengthCm)
71 fmt.Fprintf(output, "length_cm %-10T %.1f\n", landing.LengthCm, landing.LengthCm)
62 fmt.Fprintf(output, "on_ice %-12T %t\n", landing.OnIce, landing.OnIce)
72 fmt.Fprintf(output, "water_temp %-10T %.2f\n", landing.WaterTemp, landing.WaterTemp)
63 fmt.Fprintf(output, "landed_at %-12T %s\n", landing.LandedAt, landing.LandedAt.Format(time.RFC3339))
73 fmt.Fprintf(output, "on_ice %-10T %t\n", landing.OnIce, landing.OnIce)
74 fmt.Fprintf(output, "landed_at %-10T %s\n", landing.LandedAt, landing.LandedAt.Format(time.RFC3339))
75 fmt.Fprintf(output, "landed_on %-10T %s\n", landing.LandedOn, landing.LandedOn.Format(time.DateOnly))
76 fmt.Fprintf(output, "catch_id %-10T %s\n", landing.CatchID, landing.CatchID)
77 fmt.Fprintf(output, "auction_lot %-10T %s\n", landing.AuctionLot, landing.AuctionLot)
78 // %T prints []byte as []uint8, since byte is an alias for uint8.
64 // %T prints []byte as []uint8, since byte is an alias for uint8.
79 fmt.Fprintf(output, "tag %-10T % x\n", landing.Tag, landing.Tag)
65 fmt.Fprintf(output, "tag %-12T % x\n", landing.Tag, landing.Tag)
80 fmt.Fprintf(output, "notes %-10T %s\n", landing.Notes, *landing.Notes)
66 fmt.Fprintf(output, "notes %-12T %s\n", landing.Notes, *landing.Notes)
67 fmt.Fprintf(output, "berth %-12T %d\n", landing.Berth, landing.Berth)
68 fmt.Fprintf(output, "price_per_kg %-12T %s\n", landing.PricePerKg, landing.PricePerKg.String())
81 return nil
69 return nil
82}
70}