91 lines
2.2 KiB
SQL
91 lines
2.2 KiB
SQL
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-- Practical SQL: A Beginner's Guide to Storytelling with Data, 2nd Edition
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-- by Anthony DeBarros
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-- Chapter 4 Code Examples
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----------------------------------------------------------------------------
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-- Listing 4-1: Character data types in action
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CREATE TABLE char_data_types (
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char_column char(10),
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varchar_column varchar(10),
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text_column text
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);
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INSERT INTO char_data_types
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VALUES
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('abc', 'abc', 'abc'),
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('defghi', 'defghi', 'defghi');
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COPY char_data_types TO 'C:\YourDirectory\typetest.txt'
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WITH (FORMAT CSV, HEADER, DELIMITER '|');
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-- Listing 4-2: Number data types in action
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CREATE TABLE number_data_types (
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numeric_column numeric(20,5),
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real_column real,
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double_column double precision
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);
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INSERT INTO number_data_types
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VALUES
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(.7, .7, .7),
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(2.13579, 2.13579, 2.13579),
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(2.1357987654, 2.1357987654, 2.1357987654);
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SELECT * FROM number_data_types;
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-- Listing 4-3: Rounding issues with float columns
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-- Assumes table created and loaded with Listing 4-2
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SELECT
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numeric_column * 10000000 AS fixed,
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real_column * 10000000 AS floating
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FROM number_data_types
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WHERE numeric_column = .7;
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-- Listing 4-4: Timestamp and interval types in action
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CREATE TABLE date_time_types (
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timestamp_column timestamp with time zone,
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interval_column interval
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);
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INSERT INTO date_time_types
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VALUES
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('2022-12-31 01:00 EST','2 days'),
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('2022-12-31 01:00 PST','1 month'),
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('2022-12-31 01:00 Australia/Melbourne','1 century'),
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(now(),'1 week');
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SELECT * FROM date_time_types;
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-- Listing 4-5: Using the interval data type
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-- Assumes script 4-4 has been run
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SELECT
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timestamp_column,
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interval_column,
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timestamp_column - interval_column AS new_date
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FROM date_time_types;
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-- Listing 4-6: Three CAST() examples
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SELECT timestamp_column, CAST(timestamp_column AS varchar(10))
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FROM date_time_types;
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SELECT numeric_column,
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CAST(numeric_column AS integer),
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CAST(numeric_column AS text)
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FROM number_data_types;
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-- Does not work:
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SELECT CAST(char_column AS integer) FROM char_data_types;
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-- Alternate notation for CAST is the double-colon:
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SELECT timestamp_column::varchar(10)
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FROM date_time_types;
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