MS SQL Basics Tutorial: Annotation characters, operators, and wildcard characters

4.5.1 annotation character (Annotation)

Two types of annotation characters can be used in Transact-SQL.

The ANSI standard annotation character "--" is used for single-line annotations;

The same as the C language of the program annotation symbol, that is, "/**/". "/*" is used for the beginning of the annotation text, "*/" for the end of the comment text, you can identify multiple lines of text in the program as comments.

4.5.2 operator (Operator)

1 Arithmetic operators

Includes: + (plus),-(minus), (multiply), (except),% (take more)

2 comparison operators

Includes:> (greater than) < (less than), = (equals), >= (greater than or equal), <= (less than equal), <>

(Not equal to),!= (not equal to),!> (not greater than)!< (not less than)

Where!=,!>,!< are not ANSI-standard operators.

3 logical operators

Include: and (with), or (or), not (non)

4-bit operator

Includes: Bitwise AND, | (bitwise OR), ~ (bitwise NOT) ^ (bitwise XOR)

5 Connection Operators

The join operator "+" is used to concatenate a mixture of two or more characters or binary strings, column names, or strings and columns, adding a string to the end of another string. The syntax is as follows:

<expression1>+<expression2>

Example 4-7

Use Pangu

Declare@startdate datetime

Set@startdate= ' 1/1/2000 '

Select ' Start Date: ' +convert (varchar @startdate)

The--convert () function is used to convert the data type, see 4.8.4

The results of the operation are as follows:

Start Date:jan 1 2000

Example 4-8:

Use Pangu

Select ' The highest salary of the employee is: ' + e_name+ ' monthly salary: ' +convert (varchar) e_wage

From employee

where e_wage=

(select Max (e_wage)

From employee)

The results of the operation are as follows:

The employee with the highest monthly salary is: John Monthly salary is 8000.00

(1 row (s) affected)

In Transact-SQL, operators are processed in the following order, if the same-level operations appear together, the order bits are processed from left to right.

bracket () bitwise operator ~ arithmetic operator *,/,% arithmetic operator +,-bitwise operator ^ bit operator & Bitwise operator | Logical operators not logical operators and logical operators OR

4.5.3 wildcard character wildcard

You can use the wildcard characters shown in table 4-4 in SQL Server.

Table 4-4 Transact-SQL wildcard characters

See the full set of "MS SQL Basics Tutorials"