mysql field

Many business tables use design patterns that violate the first paradigm due to historical or performance reasons. That is, multiple attribute values are stored in the same column (the specific structure is shown in the table below ). In this mode,

Use two functions: length and char_length. Length: the length of a calculated field. A Chinese character is counted as three characters. A number or letter is counted as one character. Char_length: whether it is a Chinese character, a number, or a

The number of split fields must be limited. Therefore, it is impossible to store an infinite number of characters in a string.The table to which this field belongs is associated with this field. It must be a one-to-many relationship.For example, the

Storage required for column type TINYINT1 byte SMALLINT2 MEDIUMINT3 byte INT4 byte INTEGER4 byte BIGINT8 byte FLOAT (X) 4 if X Storage required for column type TINYINT 1 byte SMALLINT 2 byte MEDIUMINT 3 byte INT 4 byte INTEGER 4 byte BIGINT 8 byte

MySQL supports a large number of column types, which can be divided into three types: Number type, date and time type, and string (character) type. This section first provides an overview of available types, summarizes the storage requirements for

MySQL supports a large number of column types, which can be divided into three types: Number type, date and time type, and string (character) type. This section first provides an overview of available types, summarizes the storage requirements for

Storage required for column type TINYINT 1 byte SMALLINT 2 byte MEDIUMINT 3 byte INT 4 byte INTEGER 4 byte BIGINT 8 byte FLOAT (X) 4 if X

MySQL supports a large number of column types, which can be divided into three types: Number type, date and time type, and string (character) type. This section first provides an overview of available types, summarizes the storage requirements for

MySQL supports a large number of column types, which can be divided into three types: number type, date and time type, and string (character) type. This section first provides an overview of available types, summarizes the storage requirements for

There is a field that can store integers and decimals, such as 43 and 43 thousand yuan. how can I set a field that can store integers and decimals, such as 43 and 43 thousand yuan, can be saved, how should I set Reply content: There is a field

Example: tinyint (1) description: I understand that the maximum positive number of the Tinyint type is 255. What I don't understand is the purpose of setting 1 here. In fact, even if the length is set to 1, you can store any number greater than one

Problem: When modifying house information, one field is the total number of floors floorall, which is an int field, allowing nullWhen the information is modified, if the value of this field is entered, a value is written to the database and Null

When updating records, mysql must add new values on the original values. For example, there was a record: Id Country A784829a-c0dc-4cb6-88a9-8c376fab83a6 USA       Update the country field now: Add "$ + $ UK" based on

The column types supported by MySQL are listed below. Below Code Letters are used in the description: MSpecifies the maximum display size. The max valid display size is 255.DApplicable to the floating point type and the number of digits

Add front, suffix concat, string replace replace Add prefix UPDATE ' table ' SET field_name = concat ("prefix", field_name); Add suffix UPDATE ' table ' SET field_name = concat (field_name, "suffix"); Bulk replacement UPDATE ' table ' SET

Add, modify, delete functions in the MySQL tutorial ALTER TABLE tabelname add new_field_id int (5) unsigned default 0 NOT NULL auto_increment, add primary key (NEW_FIELD_ID); Add a new column ALTER TABLE T2 add d timestamp;ALTER TABLE infos add

TINYINT -128–127 TINYINT UNSIGNED 0–255 SMALLINT -32768–32767 SMALLINT UNSIGNED 0–65535 Mediumint -8388608–8388607 Mediumint UNSIGNED 0–16777215 INT or INTEGER -2147483648–2147483647 INT UNSIGNED or INTEGER UNSIGNED 0–4294967295

MySQL supports a large number of column types, which can be grouped into 3 categories: numeric types, date and time types, and string (character) types. This section first gives an overview of the available types, summarizes the storage requirements

Today, the Chinese blog Alliance has bo friends feedback, zgboke.com can not submit blog, I was just ready to go to the Holiday Plaza Party, on the rush to submit a trial, found that the blog submitted when the following error is reported: Tip

MySQL supports a large number of column types, which can be grouped into 3 categories: numeric types, date and time types, and string (character) types. This section first gives an overview of the available types, summarizes the storage requirements