How to use additions, deletions and modifications in PHP?

We have learned so much about PHP, but I wonder how you use additions, deletions and modifications in PHP? Have you fully mastered it? If not, then follow this article to continue learning

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Insert data (increment):

Multiple syntax forms:

Form 1:

insert [into]表名〔（字段名1，字段名2 ...）] valucs (值表达式1，值表达式2 ...）.(...)...

This is the most commonly used broadcast statement. Multiple rows of data can be inserted at one time, separated by commas:

Insert statement, it should be understood that each data insertion is in "row" units. Perform insertion.

It is generally not recommended to omit the field name. The subsequent "value list" should be "one-to-one" corresponding to the field name list.

The value expression can be a "direct", Or "function call result", or variable value; among them, if the corresponding field is a character or time type, the direct value should use single quotes,

Form 2:

replacinto]表名〔(字段名1,字段名2 ...] values (值表达式1，值表达式2. ... (...….）

It is almost the same as insert into: the only difference is that if the primary key or unique key of the inserted data is "duplicate", then it will become "modify the row of data",

The following demonstrates the repalce into statement:

insert into tab_zhujian2 values(1，"bb');//这行不行，报错replace into tab_zhujian2 values(1，"bb');

Form 3:

insert [into]表名〔(字段名1，字段名2，..... ] sclect字段名1，字段名2 .. from 其他表名,

Insert the result data (possibly multiple items) queried by the select statement into the specified table.

Among them, you also need to pay attention to the correspondence of fields: the field list selected must be "one-to-one" corresponding to the field list specified previously

The following demonstrates insert into. ... select ... statement:

insert into tab_zhujian1 select * from tab_zhujian2;

Form 4:

insert [into]表名 set字段名1=值表达式1，字段名2=值表达式2，....

Delete data (delete):

Grammar form:

delete from table name [where condition] [order by sorting field] [limit limited number of rows]﹔

Note:

1, deleting data is still done in "row" units,

2, usually deleting data requires a where condition, otherwise all data will be deleted (this is very uncomfortable) Common),

3, the syntax of where condition is the same as that in select,

4, order by sorting setting, used to specify the deletion order of these data; it is usually combined with limit It only makes sense to use;

5, limit limit is used to set how many rows to delete (in the order set by orderby),

6, in actual applications, orderby and orderby are usually rarely used limit, then the conventional usage form of deletion becomes:

delete from table name where condition;

Modify data (change)

Grammar form:

update表名set字段1=值1，字段2=值2，...---

[where condition] [order by sorting field] [limit limit number of rows]

Description:

1, usually, The update statement also requires a where condition, otherwise: all data will be modified (this is rare), 2, the syntax of the where condition is the same as the syntax in select;

3, order by is used to set The order of modification and limit are used to set the number of rows to be modified. They are usually used in combination (although they are rarely used)

4. In actual applications, ordeby and limit are usually rarely used, then modify the data. The conventional usage form becomes:

update table name set field 1 = value 1, field 2 = value 2, ..... where condition

5, note: among them "Data value", if it is a "direct value" of string or time type, single quotes should be used;

for example;

update tab1 setname= 张三丰',age = 18, birthday ='1900-3-4’where id = 3;update tab1 setname =get_name(，age = fmc10，birthday = nowOwhere id = 3;

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