-- Get the number of entries in a map
SELECT cardinality(r['map_col']) AS size
FROM duckdb.query(' SELECT MAP([''a'', ''b'', ''c''], [1, 2, 3]) AS map_col ') r;
-- Returns: 3

-- Empty map
SELECT cardinality(r['map_col']) AS size
FROM duckdb.query(' SELECT MAP([], []) AS map_col ') r;
-- Returns: 0

-- Get value for a specific key
SELECT element_at(r['map_col'], 'a') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: {1}

-- Non-existent key
SELECT element_at(r['map_col'], 'c') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: {}

-- Merge two maps
SELECT map_concat(r1['map1'], r2['map2']) AS merged
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map1 ') r1,
     duckdb.query(' SELECT MAP([''b'', ''c''], [3, 4]) AS map2 ') r2;
-- Returns: {a=1, b=3, c=4}

-- Note: 'b' value from map2 (3) overwrites map1's value (2)

-- Check if key exists
SELECT map_contains(r['map_col'], 'a') AS has_key
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: t (true)

-- Check for non-existent key
SELECT map_contains(r['map_col'], 'c') AS has_key
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: f (false)

-- Check if key-value pair exists
SELECT map_contains_entry(r['map_col'], 'a', 1) AS has_entry
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: t (true)

-- Check with wrong value for existing key
SELECT map_contains_entry(r['map_col'], 'a', 2) AS has_entry
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: f (false)

-- Check if value exists
SELECT map_contains_value(r['map_col'], 1) AS has_value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: t (true)

-- Check for non-existent value
SELECT map_contains_value(r['map_col'], 3) AS has_value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: f (false)

-- Get all key-value pairs as structs
SELECT map_entries(r['map_col']) AS entries
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: {"(a,1)","(b,2)"}

-- Access individual struct fields
SELECT unnest(map_entries(r['map_col'])) AS entry
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;

-- Extract value from a map
SELECT map_extract(r['map_col'], 'a') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: {1}

-- Extract non-existent key
SELECT map_extract(r['map_col'], 'c') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: {}

-- Extract single value (not as array)
SELECT map_extract_value(r['map_col'], 'a') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: 1

-- Non-existent key returns NULL
SELECT map_extract_value(r['map_col'], 'c') AS value
FROM duckdb.query(' SELECT MAP([''a'', ''b''], [1, 2]) AS map_col ') r;
-- Returns: NULL

-- Create map from array of structs
SELECT map_from_entries(r['entries']) AS new_map
FROM duckdb.query('
    SELECT [{''k'': ''a'', ''v'': 1}, {''k'': ''b'', ''v'': 2}] AS entries
') r;
-- Returns: {a=1, b=2}

-- This is the inverse operation of map_entries
SELECT map_from_entries(map_entries(r['map_col'])) AS reconstructed
FROM duckdb.query(' SELECT MAP([''x'', ''y''], [10, 20]) AS map_col ') r;
-- Returns: {x=10, y=20}

-- Get all keys from a map
SELECT map_keys(r['map_col']) AS keys
FROM duckdb.query(' SELECT MAP([''a'', ''b'', ''c''], [1, 2, 3]) AS map_col ') r;
-- Returns: {a,b,c}

-- Empty map
SELECT map_keys(r['map_col']) AS keys
FROM duckdb.query(' SELECT MAP([], []) AS map_col ') r;
-- Returns: {}

-- Get all values from a map
SELECT map_values(r['map_col']) AS values
FROM duckdb.query(' SELECT MAP([''a'', ''b'', ''c''], [1, 2, 3]) AS map_col ') r;
-- Returns: {1,2,3}

-- Empty map
SELECT map_values(r['map_col']) AS values
FROM duckdb.query(' SELECT MAP([], []) AS map_col ') r;
-- Returns: {}

-- Approximate distinct count of customer IDs
SELECT approx_count_distinct(customer_id) FROM orders;

-- Compare with exact count
SELECT
    approx_count_distinct(customer_id) AS approx_distinct,
    COUNT(DISTINCT customer_id) AS exact_distinct
FROM orders;

-- Sample 10% of rows from a table
SELECT * FROM large_table TABLESAMPLE SYSTEM(10);

-- Sample approximately 1000 rows
SELECT * FROM events TABLESAMPLE SYSTEM(1000 ROWS);

-- Sample from data lake files
SELECT * FROM read_parquet('s3://datalake/**/*.parquet') TABLESAMPLE SYSTEM(5);

-- Use sampling for quick data profiling
SELECT
    region,
    COUNT(*) AS sample_count,
    AVG(revenue) AS avg_revenue
FROM sales_data TABLESAMPLE SYSTEM(2)
GROUP BY region;

-- Sample from joins for performance
SELECT c.name, COUNT(o.id) AS order_count
FROM customers c
JOIN orders o TABLESAMPLE SYSTEM(10) ON c.id = o.customer_id
GROUP BY c.name;

-- System sampling (recommended for large tables)
SELECT * FROM huge_table TABLESAMPLE SYSTEM(1);

-- Bernoulli sampling (exact percentage)
SELECT * FROM medium_table TABLESAMPLE BERNOULLI(5);

-- Group events by hour
SELECT time_bucket(INTERVAL '1 hour', created_at) AS hour_bucket, COUNT(*)
FROM events
GROUP BY hour_bucket
ORDER BY hour_bucket;

-- Group by 15-minute intervals
SELECT time_bucket(INTERVAL '15 minutes', timestamp_col), AVG(value)
FROM sensor_data
WHERE timestamp_col >= '2024-01-01'
GROUP BY 1
ORDER BY 1;

-- Format current timestamp
SELECT strftime(NOW(), '%Y-%m-%d %H:%M:%S') AS formatted_time;

-- Format timestamps in different formats
SELECT
    order_id,
    strftime(created_at, '%Y-%m-%d') AS order_date,
    strftime(created_at, '%H:%M') AS order_time,
    strftime(created_at, '%A, %B %d, %Y') AS readable_date
FROM orders;

-- Use for partitioning file exports
COPY (SELECT * FROM events WHERE event_date = '2024-01-01')
TO 's3://bucket/events/' || strftime('2024-01-01'::timestamp, '%Y/%m/%d') || '/events.parquet';

-- Parse date strings
SELECT strptime('2024-01-15 14:30:00', '%Y-%m-%d %H:%M:%S') AS parsed_timestamp;

-- Parse different formats
SELECT
    strptime('Jan 15, 2024', '%b %d, %Y') AS date1,
    strptime('15/01/2024', '%d/%m/%Y') AS date2,
    strptime('2024-01-15T14:30:00Z', '%Y-%m-%dT%H:%M:%SZ') AS iso_date;

-- Parse log timestamps
SELECT
    log_id,
    strptime(timestamp_string, '%Y-%m-%d %H:%M:%S') AS parsed_time,
    message
FROM raw_logs;

-- Get current epoch time
SELECT epoch(NOW()) AS current_epoch;

-- Convert timestamps for API usage
SELECT
    event_id,
    epoch(event_timestamp) AS epoch_seconds
FROM events;

-- Filter using epoch time
SELECT * FROM events
WHERE epoch(created_at) > 1640995200; -- After 2022-01-01

-- High-precision timestamp for JavaScript
SELECT epoch_ms(NOW()) AS timestamp_ms;

-- For time-series data
SELECT
    sensor_id,
    epoch_ms(reading_time) AS timestamp_ms,
    value
FROM sensor_readings;

-- Convert epoch milliseconds to timestamp
SELECT epoch_ms(1640995200000) AS timestamp_from_ms; -- 2022-01-01 00:00:00

-- Convert stored milliseconds back to timestamps
SELECT
    event_id,
    epoch_ms(timestamp_ms) AS event_time
FROM events;

-- Microsecond precision timestamps
SELECT epoch_us(NOW()) AS timestamp_us;

-- Nanosecond precision timestamps
SELECT epoch_ns(NOW()) AS timestamp_ns;

-- Create timestamp from current epoch microseconds
SELECT make_timestamp(epoch_us(NOW())) AS reconstructed_timestamp;

-- Create specific timestamps
SELECT make_timestamp(1640995200000000) AS new_years_2022; -- 2022-01-01 00:00:00

-- Create timestamptz from current epoch microseconds
SELECT make_timestamptz(epoch_us(NOW())) AS reconstructed_timestamptz;

-- Create specific timestamptz
SELECT make_timestamptz(1640995200000000) AS new_years_2022_tz;

  SELECT duckdb.install_extension('iceberg');
  SELECT duckdb.install_extension('avro', 'community');

  GRANT ALL ON FUNCTION duckdb.install_extension(TEXT, TEXT) TO my_admin;

SELECT duckdb.load_extension('iceberg');

-- Disable auto-loading for an extension
SELECT duckdb.autoload_extension('iceberg', false);

-- Enable auto-loading for an extension
SELECT duckdb.autoload_extension('iceberg', true);

This command puts the FROM clause before the SELECT command and uses a list comprehension. Both of these features are not supported in Postgres Pro.

  SELECT * FROM duckdb.query('FROM range(10) AS a(a) SELECT [a for i in generate_series(0, a)] as arr');