null mysql

MySQL Reference Manual for version 4.1.0-alpha. -------------------------------------------------------------------------------- 6.8 MySQL full-text search Up to 3.23.23, MySQL began to support full-text indexing and searching. Full-text index is a

ASCII (str)Returns the ASCII value of the first character of the string 'str' (0 is returned when 'str' is an empty string)Mysql> selectASCII ('2 ');-> 50Mysql> select ASCII (2 );->50Mysql> select ASCII ('dete ');-> 100ORD (str)If the string 'str'

Full-text index is a Fulltext index in MySQL. Fulltext index is used for MyISAM tables.Use alter table or createIndex is created on char, varchar, or text columns. For large databases, load data to a table without Fulltext indexes, and then use

For SQL beginners, the concept of NULL is often confused. They often think that NULL is the same as the NULL string. This is not the case. For example, the following statements are completely different: Mysql> insert into my_table (phone) VALUES

Full-text index is a FULLTEXT index in MySQL. FULLTEXT indexes are used for MyISAM tables. you can use ALTERTABLE or CREATEINDEX to create indexes in CHAR, VARCHAR, or TEXT columns at or after CREATETABLE. For large databases, load data to a table

Processing the ten NULL values of MySQ learning notes is a special feature of MySQL. In concept, NULL means "no value" or "unknown value", and it is regarded as a slightly different value. To test NULL, you cannot use arithmetic comparison

From: http://lz12366.iteye.com/blog/673290 The concept of null value is a common cause of confusion among SQL beginners. They often think that null is the same as an empty string. No! For example, the following statements are completely different:

We often see MySQL NULL strings and NULL values, but they are not a concept. The following describes the differences between NULL and MySQL NULL strings for your reference. For SQL beginners, the concept of NULL value is often confusing. They often

MySQL Reference Manual for version 4.1.0-alpha. -------------------------------------------------------------------------------- 6.8 MySQL Full-Text Search At 3.23.23, MySQL began to support Full-text indexing and searching. Full-text indexing

The creation of libraries, tables, and query statements in MySQL is very helpful for us to use the database in the future, this article is a summary of these basic statements, I hope it will help you 1. Create and delete databases Creating a

MySQL automatically transforms numbers into strings when necessary, and vice versa:Mysql> Select 1+ "1"; -2 mysql> SELECT CONCAT (2, ' test '); ' 2 test 'If you want to explicitly transform a number into a string, pass it as an argument CONCAT() .If

String functionsASCII (str)Returns the ASCII value of the first character of the string str (str is empty when the string returns 0)Mysql> Select ASCII (' 2 ');50Mysql> Select ASCII (2);50Mysql> Select ASCII (' dete ');100ORD (str)If the string str

For beginners of SQL, the concept of null values often creates confusion, and they often assume that null is the same thing as an empty string. This is not the case. For example, the following statements are completely different: Mysql> INSERT into

NULL and NOT NULL modifiers: You can add this null or NOT NULL modifier to each field to specify whether the field can be empty (null), or you must fill in the data (not NULL). mysql specifies null modifiers by default, and if a field is specified

MySQL Full-Text Search At 3.23.23, MySQL began to support Full-text indexing and searching. Full-text indexing is an fulltext type index in MySQL. The fulltext index is used for MyISAM tables, which can be created on a CHAR, VARCHAR, or TEXT column

For beginners of SQL, the concept of null values often creates confusion, and they often assume that null is the same thing as an empty string. This is not the case. For example, the following statements are completely different: Mysql> INSERT into

Full-text indexing is an fulltext type index in MySQL. The fulltext index is used for MyISAM tables, which can be created on a char, varchar, or text column by using ALTER TABLE or CREATE index at or after the CREATE table. For large databases, it

In MySQL, each field definition contains additional constraints or modifiers that can be used to increase the constraints on the input data. Today, let's take a look at MySQL field constraints:NULLAndNot

1. Arithmetic operatorsAddMysql> Select 1+2;ReducingMysql> Select 2-1;ByMysql> Select 2*3;ExceptMysql> Select 5/3;BusinessMysql> SELECT 5 DIV 2;ModeMysql> Select 5%2,mod (5,2);2. Comparison operatorsEqualsMysql> Select 1=0,1=1,null=null;Not equal

MySQL floating-point and fixed-point types can be expressed by the type name plus (M, D). M indicates the total length of the 20540; D indicates the length after the decimal point, M and D are also called precision and scale. for example, float (9999