MySQL database operations 5-common operators

Overview:

Common operators include:

Arithmetic operators,

comparison operators,

logical operators,

Bitwise manipulation Operators

etc...

1. Arithmetic operators:

Supports +–*/and%,

For example, when looking for data, use:

Select n+1, n+2 from Num;

Before:, after:

You can also use other operations.

Note that the Division will take four digits after the decimal point. The result of the addition of 0 is meaningless null.

2. Comparison operators

The comparison operator returns a result that is typically 9, 1, or null, which can be used in query statements to query for records that satisfy a condition.

Common comparison operators are described in:

=

Select 1=0,2=2,'1'=1,1+2=3+0,NULL=NULL;

The result is:

Because = is not used for null judgments, the last result is null and cannot be judged.

Same usage, not equal to <> or! =, less than or equal to <=, less than <, greater than or equal to >=, greater than; Note These operators can also compare strings and compare them in the order in which they are arranged.

Is null, ISNULL (), or is not NULL

Determines whether a value is empty.

Such as:

Select NULL  is null,isnull(nullis notnull;

The result is:

Between and

Determine if there is a range, such as

Select 4 between 3  and ten;

Results:

Note String types are range-compared in the order of the character descriptor.

Such as:

Select ' F ' between ' a '  and ' g ';

Results:

LEAST (value 1, value 2, ...)

Returns the minimum value, but returns null if there is null in the value, such as:

Select Least (ten,3.0,+), least (4);

The result is:

When comparing strings, it is also the smallest string to be compared, such as:

Select least ('abc','abd',' ABCD ');

Results:

Greatest

In contrast to least, the maximum value is compared. Such as:

Select Greatest ('abc','abd','ABCD  ');

The result is:

In,not in

Determine if the value is in the list, such as:

Select 4 inch(1,4,'R','T'),'R'  not inch(1,4,'R','T');

The result is:

Null is returned when the left side is null or if no match is found and there is null in the list.

Like

Pseudo-Regular match, only supports the two wildcard characters% and _,% means match any number of characters, _ matches any single character.

Such as:

Select ' Student '  like ' st% ';

The result is:

As you can see, the string following the like is a regular expression, preceded by a string to be matched.

Regexp

The regular expression matches, ^ matches the beginning, the $ matches the end,. Match single character, [] match the characters in it (supported with-specified range), * match its preceding characters any number of times (I disagree when using *, because there may be problems when using *).

Such as:

Select ' Ssky ' ' [AB] ','Ssky's*';

The result is:

If by definition, the s* match does not match the KY, but the result is a return to True (1). Please advise me if you have any knowledge.

3. Logical Operators

Not OR!

When the operand is 1 at 0 and 0 is 1, the inverse is taken, such as:

Select  not (1),not0 ,! True

The result is:

And OR &&

and operation;

Such as:

Select 1  and 1,0and1;

Results:

OR OR | |

or operation;

Such as:

Select 1 or 1,0| | 1;

Results:

Xor

(The same is 0, the difference is 1)

Such as:

Select 0 0;

Results:

4. Bitwise operators (slightly).

Because bit operations are mainly used with binary, the occasion is special, so I do not remember for the time being, but the MySQL-supported bitwise operators have

| Bit or

& Bit and

^ Bit XOR or

<< left-shift

>> bit Right Shift

-To-take counter

MySQL database operations 5-common operators