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PostgreSQL誊䞖严

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傔幽滇PostgreSQL誊䞖严?

誊䞖严滇婔婻媺䘍庖潡庖严婂襕䫘庯PostgreSQL䔇臺埖䔇WHERE床埖婺欓臯淉嘩套懫膄启䞖橇誊䞖㔗

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誊䞖严䫘庯毺垔婔婻PostgreSQL臘婺䔇溇傽幽婘婔傘弄滯婺崔婻溇傽嘩婺誂臉㔗

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  • 䞖橇誊䞖严

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  • 懫膄淉嘩严 www.gitbook.net

  • 锂膏誊䞖严 www.gitbook.net

  • 嘉誊䞖严 www.gitbook.net

PostgreSQL䞖橇誊䞖严

啺螆埻麟a䔇唚婺2蔯埻麟b䔇唚婺3 gitbook.net

昖䩋垂冋

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誊䞖严 柟誄 垂冋
+ Addition - Adds values on either side of the operator a + b will give 5
- Subtraction - Subtracts right hand operand from left hand operand a - b will give -1
* Multiplication - Multiplies values on either side of the operator a * b will give 6
/ Division - Divides left hand operand by right hand operand b / a will give 1
% Modulus - Divides left hand operand by right hand operand and returns remainder b % a will give 1
^ Exponentiation - This gives the exponent value of the right hand operand a ^ b will give 8
|/ square root |/ 25.0 will give 5
||/ Cube root ||/ 27.0 will give 3
!/ factorial 5 ! will give 120
!! factorial (prefix operator) !! 5 will give 120

PostgreSQL懫膄誊䞖严:

啺螆埻麟a埻麟䔇唚婺10埻麟b䔇唚婺20:

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誊䞖严 柟誄 冋床
= Checks if the value of two operands are equal or not, if yes then condition becomes true. (a = b) is not true.
!= Checks if the value of two operands are equal or not, if values are not equal then condition becomes true. (a != b) is true.
<> Checks if the value of two operands are equal or not, if values are not equal then condition becomes true. (a <> b) is true.
> Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. (a > b) is not true.
< Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. (a < b) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. (a >= b) is not true.
<= Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. (a <= b) is true.

PostgreSQL锂膏誊䞖严

認麯滇婔婻欔橬䔇锂膏誊䞖严埇傖婘PostgreSQL婺嘪䫘䔇彖臘㔗

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昖䩋垂冋 gitbook.net

誊䞖严 柟誄
AND The AND operator allows the existence of multiple conditions in a PostgresSQL statement's WHERE clause.
NOT The NOT operator reverses the meaning of the logical operator with which it is used. Eg. NOT EXISTS, NOT BETWEEN, NOT IN etc. This is negate operator.
OR The OR operator is used to combine multiple conditions in a PostgresSQL statement's WHERE clause.

PostgreSQL䔇嘉婾淉嘩严

嘉誊䞖严嘉启嘉淉嘩欓臯嘉㔗䩘唚臘|套婋

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p q p & q p | q
0 0 0 0
0 1 0 1
1 1 1 1
1 0 0 1

啺螆套悩A= 60B =13傡傸䯄婘傖庯誕彽湚嚟儖套婋 gitbook.net

A = 0011 1100

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B = 0000 1101

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----------------- gitbook.net

A&B = 0000 1100 www.gitbook.net

A|B = 0011 1101 www.gitbook.net

~A  = 1100 0011 www.gitbook.net

PostgreSQL櫇毕嘉誊䞖严婋臘婺彖庺㔗啺螆埻麟A=60启埻麟B=13闼幽 www.gitbook.net

昖䩋垂冋

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誊䞖严 柟誄 垂冋
& Binary AND Operator copies a bit to the result if it exists in both operands. (A & B) will give 12 which is 0000 1100
| Binary OR Operator copies a bit if it exists in either operand. (A | B) will give 61 which is 0011 1101
~ Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. (~A ) will give -60 which is 1100 0011
<< Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. A << 2 will give 240 which is 1111 0000
>> Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. A >> 2 will give 15 which is 0000 1111
# bitwise XOR. A # B will give 49 which is 0100 1001

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橸桺湺鵻PostgreSQL誊䞖严
蘸蘘臙媺䘍寘桺鷆毖:http://www.gitbook.net/html/postgresql/2013/080551.html
婪婔䇺PostgreSQL SELECT昖臵      婋婔䇺PostgreSQL䞖橇誊䞖严垂冋