MariaDB Text,Time,Numeric Manipulation Function

MariaDB Text,Time,Numeric Manipulation Function

字符操作函数

Commonly Used Text-Manipulation Functions

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Function    Description

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Left()      Returns characters from left of string

Length()    Returns the length of a string

Locate()    Finds a substring within a string

Lower()     Converts string to lowercase

LTrim()     Trims white space from left of string

Right()     Returns characters from right of string

RTrim()     Trims white space from right of string

Soundex()   Returns a string’s SOUNDEX value

SubString() Returns characters from within a string

Upper()     Converts string to uppercase

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(jlive)[crashcourse]>SELECT vend_name, UPPER(vend_name) AS vend_name_uppercase FROM vendors ORDER BY vend_name;

+----------------+---------------------+

| vend_name      | vend_name_uppercase |

+----------------+---------------------+

| ACME           | ACME                |

| Anvils R Us    | ANVILS R US         |

| Furball Inc.   | FURBALL INC.        |

| Jet Set        | JET SET             |

| Jouets Et Ours | JOUETS ET OURS      |

| LT Supplies    | LT SUPPLIES         |

+----------------+---------------------+

6 rows in set (0.00 sec)

(jlive)[crashcourse]>SELECT cust_name, cust_contact FROM customers WHERE cust_contact = 'Y. Lie';

Empty set (0.00 sec)

(jlive)[crashcourse]>SELECT cust_name, cust_contact FROM customers WHERE Soundex(cust_contact) = Soundex('Y Lie');

+-------------+--------------+

| cust_name   | cust_contact |

+-------------+--------------+

| Coyote Inc. | Y Lee        |

+-------------+--------------+

1 row in set (0.00 sec)

“听起来”像，就匹配

时间操作函数

提示：5.3以后的版本支持microseconds

Commonly Used Date and Time Manipulation Functions

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Function Description

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AddDate() Add to a date (days, weeks, and so on)

AddTime() Add to a time (hours, minutes, and so on)

CurDate() Returns the current date

CurTime() Returns the current time

Date() Returns the date portion of a date time

DateDiff() Calculates the difference between two dates

Date_Add() Highly flexible date arithmetic function

Date_Format() Returns a formatted date or time string

Day() Returns the day portion of a date

DayOfWeek() Returns the day of week for a date

Hour() Returns the hour portion of a time

Minute() Returns the minute portion of a time

Month() Returns the month portion of a date

Now() Returns the current date and time

Second() Returns the second portion of a time

Time() Returns the time portion of a date time

Year() Returns the year portion of a date

 

-------------------------------------------------------

(jlive)[crashcourse]>SELECT order_date,cust_id,order_num FROM orders WHERE order_date = '2011-09-01';

+---------------------+---------+-----------+

| order_date          | cust_id | order_num |

+---------------------+---------+-----------+

| 2011-09-01 00:00:00 |   10001 |     20005 |

+---------------------+---------+-----------+

1 row in set (0.00 sec)

以上判断非常不安全，这一天的记录可能非常多

(jlive)[crashcourse]>SELECT order_date,cust_id,order_num FROM orders WHERE Date(order_date) = '2011-09-01';

+---------------------+---------+-----------+

| order_date          | cust_id | order_num |

+---------------------+---------+-----------+

| 2011-09-01 00:00:00 |   10001 |     20005 |

+---------------------+---------+-----------+

1 row in set (0.16 sec)

需要用Date()函数重新格式化

(jlive)[crashcourse]>SELECT order_date,cust_id,order_num FROM orders WHERE Date(order_date) BETWEEN '2011-09-01' AND '2011-09-30';

+---------------------+---------+-----------+

| order_date          | cust_id | order_num |

+---------------------+---------+-----------+

| 2011-09-01 00:00:00 |   10001 |     20005 |

| 2011-09-12 00:00:00 |   10003 |     20006 |

| 2011-09-30 00:00:00 |   10004 |     20007 |

+---------------------+---------+-----------+

 

3 rows in set (0.15 sec)

上面虽然查出了2011年9月的数据但需要人为的计算该年该月份的起点和终点，如果碰到二月这个特殊的月份就会比较费力

(jlive)[crashcourse]>SELECT order_date,cust_id,order_num FROM orders WHERE Year(order_date) = 2011 AND Month(order_date) = 9;

+---------------------+---------+-----------+

| order_date          | cust_id | order_num |

+---------------------+---------+-----------+

| 2011-09-01 00:00:00 |   10001 |     20005 |

| 2011-09-12 00:00:00 |   10003 |     20006 |

| 2011-09-30 00:00:00 |   10004 |     20007 |

+---------------------+---------+-----------+

 

3 rows in set (0.00 sec)

全部交给MariaDB自己去解读

Numeric函数

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Function Description

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Abs() Returns a number’s absolute value

Cos() Returns the trigonometric cosine of a specified angle

Exp() Returns the exponential value of a specific number

Mod() Returns the remainder of a division operation

Pi() Returns the value of pi

Rand() Returns a random number

Sin() Returns the trigonometric sine of a specified angle

Sqrt() Returns the square root of a specified number

Tan() Returns the trigonometric tangent of a specified angle

 

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