EXPLAIN Output Analysis

EXPLAIN Output Analysis is a SQL statement in the SELECT Queries category. Reading and understanding EXPLAIN output across databases to identify slow query patterns. The syntax is EXPLAIN [ANALYZE] SELECT ...;. It returns execution plan analysis. A typical example: -- MySQL: EXPLAIN output columns -- id, select_type, table, type (ALL=worst, const=best), possible_keys, key, key_len, ref, rows, Extra -- PostgreSQL: EXPLAIN ANALYZE -- Seq Scan: full table read (bad for large tables) -- Index Scan: index lookup + table access -- Index Only Scan: index covers all columns (fastest) -- Bitmap Heap Scan: bitmap index + heap access -- Nested Loop: for each outer, scan inner (good for small) --… A close relative is SELECT, which retrieves data from a table. The most fundamental SQL statement. A close relative is SELECT *, which selects all columns from a table. A close relative is SELECT DISTINCT, which returns only distinct (unique) values from the specified columns.