mysql更新语句sql_SQL更新语句说明：更新表的查询（包括
MySQL⽰例）
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mysql更新语句sql
更新查询可以做什么 (What an Update query can do)
An update query gives the DBA or SQL-using programmer the ability to update many records with one command.
更新查询使DBA或使⽤SQL的程序员能够使⽤⼀个命令更新许多记录。
Important Safety Tip: always have a backup copy of what you are about to change BEFORE you change it.
重要安全提⽰：更改之前，请始终保留要更改内容的备份副本。
This guide will:
本指南将：
add a new field to the student table手机端网页模板尺寸
向学⽣表添加新字段
test the logic to update that field with a school assigned email address
测试⽤学校分配的电⼦邮件地址更新该字段的逻辑
update the new field.
更新新字段。
Here is the student table as we start this process
这是我们开始此过程时的学⽣表
SELECT * FROM student;
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
| studentID | FullName              | sat_score | programOfStudy  | rcd_Created        | rcd_Updated        |
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
|        1 | Monique Davis          |      400 | Literature      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        2 | Teri Gutierrez        |      800 | Programming      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        3 | Spencer Pautier        |      1000 | Programming      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        4 | Louis Ramsey          |      1200 | Programming      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        5 | Alvin Greene          |      1200 | Programming      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        6 | Sophie Freeman        |      1200 | Programming      | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|        7 | Edgar Frank "Ted" Codd |      2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
|        8 | Donald D. Chamberlin  |      2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
|        9 | Raymond F. Boyce      |      2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
9 rows in set (0.00 sec)
更改表并添加新字段 (Alter the table and add a new field)
ALTER TABLE `fcc_sql_guides_database`.`student`
ADD COLUMN `schoolEmailAdr` VARCHAR(125) NULL AFTER `programOfStudy`;
The student table after the alter is executed.
执⾏更改后的学⽣表。
+------------------------+-----------+------------------+----------------+
| FullName              | sat_score | programOfStudy  | schoolEmailAdr |
+------------------------+-----------+------------------+----------------+
中学生如何学编程| Monique Davis          |      400 | Literature      | NULL          |
| Teri Gutierrez        |      800 | Programming      | NULL          |
| Spencer Pautier        |      1000 | Programming      | NULL          |
绿松石项链
| Louis Ramsey          |      1200 | Programming      | NULL          |
| Alvin Greene          |      1200 | Programming      | NULL          |
| Sophie Freeman        |      1200 | Programming      | NULL          |
| Edgar Frank "Ted" Codd |      2400 | Computer Science | NULL          |
| Donald D. Chamberlin  |      2400 | Computer Science | NULL          |
| Raymond F. Boyce      |      2400 | Computer Science | NULL          |
+------------------------+-----------+------------------+----------------+
9 rows in set (0.00 sec)
测试逻辑(⾮常重要的⼀步！) (TESTING the logic (VERY important step!))
SELECT FullName, instr(FullName," ") AS firstSpacePosition,
concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu") AS schoolEmail
FROM student;
+------------------------+--------------------+------------------------+
| FullName              | firstSpacePosition | schoolEmail            |
+------------------------+--------------------+------------------------+
| Monique Davis          |                  8 | Monique@someSchool.edu |
| Teri Gutierrez        |                  5 | Teri@someSchool.edu    |
| Spencer Pautier        |                  8 | Spencer@someSchool.edu |
| Louis Ramsey          |                  6 | Louis@someSchool.edu  |
| Alvin Greene          |                  6 | Alvin@someSchool.edu  |
mysql语句顺序| Sophie Freeman        |                  7 | Sophie@someSchool.edu  |
| Edgar Frank "Ted" Codd |                  6 | Edgar@someSchool.edu  |
| Donald D. Chamberlin  |                  7 | Donald@someSchool.edu  |
| Raymond F. Boyce      |                  8 | Raymond@someSchool.edu |
+------------------------+--------------------+------------------------+
9 rows in set (0.00 sec)
A note about concat(): in MySQL this command is used to combined strings, not so in other SQL versions (check your manual). In this usage it works like this: The substring of the FullName field up to but not including the first space is combined with “@someSchool.edu”. In the real world this would
HAVE TO be much more complex and you would need to ensure that the email address is unique.
关于concat()的注释：在MySQL中，此命令⽤于组合字符串，⽽在其他SQL版本中则不是这样(请查看⼿册)。在这种⽤法中，它的⼯作⽅式如下：FullName字段的⼦字符串，直到但不包括第⼀个空格，都与“ @ someSchool.edu”组合在⼀起。在现实世界中，这将变得更加复杂，并且您需要确保电⼦邮件地址是唯⼀的。
进⾏更新 (Doing the update)
We’ll pretend that this is what we want and update the table with this information:
我们将假装这就是我们想要的，并使⽤以下信息更新表：
UPDATE student SET schoolEmailAdr = concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu")
WHERE schoolEmailAdr is NULL;
Success!
成功！
+------------------------+-----------+------------------+------------------------+
| FullName              | sat_score | programOfStudy  | schoolEmailAdr        |
+------------------------+-----------+------------------+------------------------+
| Monique Davis          |      400 | Literature      | Monique@someSchool.edu |
| Teri Gutierrez        |      800 | Programming      | Teri@someSchool.edu    |
| Spencer Pautier        |      1000 | Programming      | Spencer@someSchool.edu |
| Louis Ramsey          |      1200 | Programming      | Louis@someSchool.edu  |
| Alvin Greene          |      1200 | Programming      | Alvin@someSchool.edu  |
| Sophie Freeman        |      1200 | Programming      | Sophie@someSchool.edu  |
| Edgar Frank "Ted" Codd |      2400 | Computer Science | Edgar@someSchool.edu  |
| Donald D. Chamberlin  |      2400 | Computer Science | Donald@someSchool.edu  |
| Raymond F. Boyce      |      2400 | Computer Science | Raymond@someSchool.edu |
+------------------------+-----------+------------------+------------------------+
9 rows in set (0.00 sec)
公众平台商城开发As with all of these SQL things there is MUCH MORE to them than what’s in this introductory guide.
与所有这些SQL事物⼀样，它们⽐本⼊门指南中的内容要多得多。
I hope this at least gives you enough to get started.
我希望这⾄少能给您⾜够的⼊门。
Please see the manual for your database manager and have fun trying different options yourself.
请参阅数据库管理员的⼿册，并尝试⾃⼰尝试其他选项，这很有趣。
您如何使⽤Update语句？ (How do you use an Update statement?)
To update a record in a table you use the  UPDATE  statement.
要更新表中的记录，请使⽤UPDATE语句。
Be careful. You can update all records of the table or just a few. Use the  WHERE  condition to specify which records do you want to update. It is possible to update one or more columns at a time. The syntax is:
⼩⼼。 您可以更新表中的所有记录或仅更新其中的⼀些记录。 使⽤WHERE条件指定要更新的记录。 可以⼀次更新⼀个或多个列。 语法为：
UPDATE table_name
SET column1 = value1,
column2 = value2, ...
WHERE condition;
Here is an example updating the Name of the record with Id 4:
这是⼀个使⽤ID 4更新记录名称的⽰例：
UPDATE Person
SET Name = “Elton John”
WHERE Id = 4;
You can also update columns in a table by using values from other tables. Use  JOIN  clause to get data from multiple tables. The syntax is:
您还可以通过使⽤其他表中的值来更新表中的列。 使⽤JOIN⼦句从多个表中获取数据。 语法为：
UPDATE table_name1
SET lumn1 = lumnA
lumn2 = lumnB
FROM table_name1
JOIN table_name2 ON table_name1.ForeignKey = table_name2.Key Here is an example updating Manager of all records:
这是所有记录的更新管理器的⽰例：
UPDATE Person
SET Person.Manager = Department.Manager
FROM Person
JOIN Department ON Person.DepartmentID = Department.ID mysql更新语句sql

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