Inzicht in Redshift-gegevenstypes en features

Introductie tot Redshift

Jason Myers

Principal Architect

Basisgegevenstypes

Numerieke types

SMALLINT, INTEGER, BIGINT
DECIMAL / NUMERIC
DOUBLE PRECISION
REAL

Datum/tijdtypes

DATE
TIME, TIMETZ
TIMESTAMP, TIMESTAMPTZ

Teksttypes

CHAR
VARCHAR

Boolean-type

BOOLEAN

Speciale gegevenstypes

SUPER-type

Semigestructureerde data
- Arrays
- Tuples
- Geneste structuren (bijv. JSON)
Gebruikt PartiQL voor verwerking
Max. grootte 16 MB

VARBYTE-type

binaire data (BLOB's)
Afbeeldingen en video's

Niet-ondersteunde PostgreSQL-types:

PostgreSQL-type	Redshift-types
DATETIME	TIMESTAMP, TIMESTAMPTZ
SERIAL	INTEGER, BIGINT
UUID	VARCHAR
JSON	SUPER, VARCHAR
ARRAY	SUPER, VARCHAR
BIT	BOOLEAN, SMALLINT, VARCHAR

Kolommen en hun gegevenstypes bekijken

-- View the column details
SELECT column_name, 
       data_type, 
       character_maximum_length AS character_max_len,
       numeric_precision, 
       numeric_scale
  -- Using a view with both internal and external schema's columns
  FROM SVV_ALL_COLUMNS 
 -- Only in the spectrumdb schema
 WHERE schema_name = 'spectrumdb'
   -- For the ecommerce_sales table
   AND table_name = 'ecommerce_sales';

Kolommen en hun gegevenstypes (vervolg)

column_name                  | data_type         | character_max_len | numeric_precision | numeric_scale
=============================|===================|===================|===================|==============
year_qtr                     | character varying | 100               | null              | null
total_sales                  | integer           | null              | 32                | 0
ecom_sales                   | integer           | null              | 32                | 0
percent_ecom                 | real              | null              | null              | null
percent_change_quarter_total | real              | null              | null              | null
percent_change_quarter_ecom  | real              | null              | null              | null
percent_change_year_total    | real              | null              | null              | null
percent_change_year_ecom     | real              | null              | null              | null

Gegevenstype-‘compatibiliteit’

Impliciete conversie: toewijzingen, vergelijkingen
Controleer de uitkomsten goed!

Van type	Naar types
CHAR	VARCHAR
DATE	CHAR, VARCHAR, TIMESTAMP, TIMESTAMPTZ
TIMESTAMP	CHAR, DATE, VARCHAR, TIMESTAMPTZ
BIGINT	BOOLEAN, CHAR, DECIMAL, DOUBLE PRECISION, INTEGER, REAL, SMALLINT, VARCHAR
DECIMAL	BIGINT, CHAR, DOUBLE PRECISION, INTEGER, REAL, SMALLINT, VARCHAR

¹ https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html#r_Type_conversion

Expliciet typen casten

CAST

-- Casting a decimal to a integer and aliasing it
SELECT CAST(2.00 AS INTEGER) AS our_int;

our_int
========
2
(1 row)

TO-functies

TO_CHAR, TO_DATE, TO_NUMBER

-- Convert the string to a date
SELECT CAST('14-01-2024 02:36:48' AS DATE) AS out_date;

date/time field value out of range: "14-01-2024 02:36:48"
HINT:  Perhaps you need a different "datestyle" setting.

-- Parse the string to a date
SELECT TO_DATE('14-01-2024 02:36:48', 'DD-MM-YYYY') AS our_date;

our_date
========
2024-01-14
(1 row)

TO-functies (vervolg)

-- Get the name of the month in a date
SELECT TO_CHAR(date '2024-01-14', 'MONTH') AS month_name;

month_name
========
JANUARY
(1 row)

Notatiestrings voor datum/tijd en numeriek

¹ https://docs.aws.amazon.com/redshift/latest/dg/r_FORMAT_strings.html

Laten we oefenen!