The problem of returning the longtext field in MySQL and its solution

Catalog

MySql in longtext Field return

As shown in the figure below

resolvent

Mysql in Text The range of the field

Chinese characters are in utf8mb4 Take up a few characters in

MySql in longtext Field return

In recent development longtext This kind of field . stay mysql The maximum length of this field in is 4G

As shown in the figure below

One of the problems encountered in development is . For example, there is a article surface , Then our page will show the data to the front end in the form of a list （ Only a few fields are displayed , As the author , Title and so on , For example, put table Multiple records are displayed in ）, But it is to find out all the information in the table , Then when the user clicks on a record , Will jump to the details page , The detailed information is displayed .

In this way, when there is a large amount of data , Or when the content of the text is relatively large , There's a problem .

Open the page , The page will always load , More data , The longer the loading time , Then the data list will be displayed . This will seriously affect the use effect .

resolvent

Certainly sql Sentence problem , When querying the whole list like the above , Can not query longtext This field , Query other fields . Then when the user clicks on a piece of data , Then according to the data id Go to the database to check this data , At this time, we will longtext Just find out .

Speaking of this , There is also a situation , Sometimes the data found in the database is encapsulated into entity classes , You can never get the value of a field , Namely null. At this time, I want to see sql sentence , Whether the returned result set encapsulates and maps this field to the corresponding field of this class .

Generally, the reason why this field is not encapsulated in the result set .

Mysql in Text The range of the field

text： Store variable length non Unicode data , Maximum length is 2^31-1 Characters .

text Column cannot have default value , During storage or retrieval , There is no case conversion , If the length is specified , No mistakes will be reported , But this length doesn't work , That means when you insert data , If it exceeds the length you specified, it can be inserted normally .

mysql in text Maximum length is 65,535(2 Of 16 Power –1) Character TEXT Column .

If you think text Not long enough , You can choose

MEDIUMTEXT Maximum length is 16,777,215.

LONGTEXT Maximum length is 4,294,967,295

Text It is mainly used to store non binary text , Such as forum posts , subject , Or Baidu knows the questions and answers .

What needs to be clear is text and char varchar blob The differences between these types .

mysql modify text Field length _mysql Of text Field length ？mysql In the database text Insufficient field length …

The type is a variable length string , most 65535 Characters ;

You can change the field type to MEDIUMTEXT( At most 16777215 Characters ) perhaps LONGTEXT( At most 4294967295 Characters ).

MySQL supports 4 TEXT field types (TINYTEXT, TEXT, MEDIUMTEXT and LONGTEXT) and this post looks at the maximum length of each of these field types.

MyISAM tables in MySQL have a maximum size of a row of 65,535 bytes, so all the data in a row must fit within that limit. However, the TEXT types are stored outside the table itself and only contribute 9 to 12 bytes towards that limit. (For more information about this refer to the MySQL Manual - Data Storage Requirements chapter). TEXT data types are also able to store much more data than VARCHAR and CHAR text types so TEXT types are what you need to use when storing web page or similar content in a database. The maximum amount of data that can be stored in each data type is as follows: TINYTEXT256 bytes

TEXT65,535 bytes~64kb

MEDIUMTEXT 16,777,215 bytes~16MB

LONGTEXT4,294,967,295 bytes~4GB

In most circumstances the TEXT type is probably sufficient, but if you are coding a content management system it’s probably best to use the MEDIUMTEXT type for longer pages to ensure there are no issues with data size limits.

Chinese characters are in utf8mb4 Take up a few characters in

answer ：3 individual

MySQL For utf8mb4 The explanation is

The existing database version defaults to utf8 All for utf8mb3, Pay attention to what it says " Same length ".

So in utf8mb4 Next , English occupation 1 Bytes , General Chinese characters account for 3 Bytes ,emoji Account for expression 4 Bytes .

About code insertion emoji Expression error , Please check Table code and Database connection Whether the code is utf8mb4.

Conclusion ： Both database and table are set to utf8mb4.

The above is personal experience , I hope I can give you a reference , I also hope you can support the software development network .