零基礎快速自學SQL,2天足矣!

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SQL??? Structured Query Language???????????????????????????????????????????????????????

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????????SQL?????????????????????SQL????????????????????Excel????????????????????w3school?????????????????????

SQL????

1?????MySQL???????phpstudy????????mysql??????????????

2???????phpstudy???phpstudy?????????????????????????

3?????Navicat??

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4???Navicat???????

??? ? ? ?????????????????????????????????????????????root????????phpstudy??mysql??????????root????????????????????

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5???????????????????????

6????5?????????

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7???sql?????

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8?????

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9?????

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1?CREATE TABLE????

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emp?
orders?

2?INSERT(??)

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??????orders?

3?UPDATE(??)

4?DELETE(??)

???delete??emp??????????????????????????????emp?id??orders?????????emp???id?????orders??????

5?DISTINCT????

???????????????????????????????????????????distinct???????????????????

???distinct?????????????*?????????? ????????????SQL?????????????name????????????????????distinct????????.

6?Select????

SELECT ??????????????????????????????????????????????90%?

SQL SELECT ??

SELECT ??? FROM ???

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SELECT * FROM ???

??????? ?LastName? ? ?FirstName? ????????? ?Persons? ??????????????? SELECT ???

SELECT LastName,FirstName FROM Persons

SELECT??????????????

SQL????

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1?AVG??

AVG ????????????NULL ?????????

2?COUNT()

COUNT( ) ????????????????

3?MAX()

MAX????????????NULL????????

4?MIN()

MIN?????????????NULL????????

5?SUM()

SUM??????????

6?ROUND()

ROUND ???????????????????

round???????

7?FORMAT()

FORMAT ???????????????

format???????

SQL????

?????????????????????SQL????????????????????

1?LIMIT

2?LIKE

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???????????????%??????????????????like ????????

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3?IN

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4?JOIN

?????JOIN???????????????????????????????????

??????????????primary key?????foreign key?????????

??????????????????????????INNER JOIN??

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  • LEFT JOIN:????????????????????
  • RIGHT JOIN????????????????????
  • FULL JOIN:????????????????

5?ALTER

??????alter??????????????alter?????

6?UNION

UNION ???????????? SELECT ???????

????UNION ??? SELECT ???????????????????????????????? SELECT ?????????????

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UNION?UNION ALL??????????????ALL???????????

??????????????????PRIMARY KEY????????????????????????

?PRIMARY KEY????????????? UNIQUE ????????????? PRIMARY KEY ???

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7?AUTO-INCREMENT(??)

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8?ORDER BY

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  • ASC:????????
  • DESC:????????

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ASC??

??DESC????????????????????SQL????

9?GROUP BY

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10?HAVING

????????????where???????????????having??????where??????????????

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11?DEFAULT

DEFAULT?????????????

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