# OBJET : SQL command
# NOTE  : SQL command are not case sensitive
# DATE  : 2020.04

# === PART1 : HOW TO QUERY ON ONE SINGLE TABLE ===

# To see all content of a table
SELECT *
FROM table

# To get number of line of a table
SELECT count(*)
FROM table

# To see content of specific field of a table
SELECT field1, field2, field3
FROM table

# To apply filter
SELECT field1, field2, field3
FROM table
WHERE ( field1 = 'abc' AND ( field2 <123 OR field3 not in ( 'x', 'y, 'z ) )

# To display new column name 
SELECT field1 AS name1, field2 AS 'name two', field3 AS name3
FROM table

# To get some statistics/volume
SELECT field1, field2, field3, count(*)
FROM table
GROUP BY field1, field2, field3

# === PART2 : HOW TO QUERY ON SEVERAL TABLES ===

# to get field from 3 table with WHERE 
SELECT t1.key1, t1.field10, t1, field.11, t2.field20, t2.field21, t3.field30
FROM table1 t1, table2 t2, table3 t3
WHERE ( (t1.key1 = t2.key2 ) AND ( t1.key1 = t3.key3 ) )

# to get field from 3 table with JOIN 
SELECT t1.key1, t1.field10, t1, field.11, t2.field20, t2.field21, t3.field30
FROM table1 t1
JOIN table2 t2 ON ( t1.key1 = t2.key2 )
JOIN table3 t3 ON ( t1.key1 = t3.key3 )

# Note : see also left join / right join / inner join


# === PART3 : PIVOT TABLE ===

# === PART 4 : HOW TO INSERT/UPDATE DATA ===

# === PART 5 : HOW TO CREATE INDEX ===