7. CRUDを操作するSQL
・データを作るINSERT文
INSERT
INTO
yokozawa_employees
VALUES
(1,
"yokozawa",
"yusuke",
31);
・データを読むSELECT
SELECT
*
FROM
yokozawa_employees
WHERE
id
=
1;
・データを更新する
UPDATE
yokozawa_employees
SET
age
=
32
WHERE
id
=
1;
・データを削除する
DELETE
FROM
yokozawa_employees
WHERE
id
=
1;
8. より複雑なデータを取り扱う
・曖昧な絞込条件
SELECT
*
FROM
customers
WHERE
email
LIKE
'%yokozawa@itandi.co.jp%';
・複数条件
SELECT
*
FROM
customer_contacts
WHERE
room_id
IS
NOT
NULL
AND
customer_id
=
4256
;
9. より複雑なデータを取り扱う
・集計、ソート
SELECT
customer_id,
count(*)
FROM
customer_contacts
GROUP
BY
customer_id
ORDER
BY
count(*)
DESC
;
・結合
SELECT
c.created_at
,cs.first_contact_at
,TO_DAYS(cs.first_contact_at)
-‐
TO_DAYS(c.created_at)
FROM
customers
as
c
INNER
JOIN
customer_statuses
cs
ON
c.id
=
cs.customer_id
;