**View Statistics (PostgreSQL):**

-- View all statistics for a table

SELECT * FROM pg_stats WHERE tablename = 'orders';

-- View specific column statistics

SELECT

attname AS column_name,

n_distinct,

most_common_vals,

most_common_freqs,

histogram_bounds,

correlation,

null_frac

FROM pg_stats

WHERE tablename = 'orders' AND attname = 'status';

-- View table-level statistics

SELECT

relname AS table_name,

reltuples AS estimated_rows,

relpages AS pages

FROM pg_class

WHERE relname = 'orders';

**Check Estimation Accuracy:**

-- Compare estimated vs actual rows

EXPLAIN ANALYZE

SELECT * FROM orders WHERE status = 'active';

-- Output shows:

-- Seq Scan on orders (cost=0..10000 rows=800000)

-- (actual time=0.1..50.2 rows=900000)

-- Estimated: 800K, Actual: 900K, Error: 1.125x

**Update Statistics:**

-- Update all statistics

ANALYZE orders;

-- Update specific columns

ANALYZE orders (status, created_at);

-- Increase statistics detail

ALTER TABLE orders ALTER COLUMN status SET STATISTICS 1000;

ANALYZE orders;

**Extended Statistics (Correlated Columns):**

-- Create dependency statistics

CREATE STATISTICS city_state_deps (dependencies)