Select
用途:
從指定表中取出指定的列的數(shù)據(jù)
語法:
SELECT column_name(s) FROM table_name
|
解釋:
從數(shù)據(jù)庫中選取資料列,并允許從一或多個(gè)資料表中,選取一或多個(gè)資料列或資料行。SELECT 陳述式的完整語法相當(dāng)復(fù)雜,但主要子句可摘要為:
SELECT select_list
[ INTO new_table ]
FROM table_source
[ WHERE search_condition ]
[ GROUP BY group_by_expression ]
[ HAVING search_condition ]
[ ORDER BY order_expression [ ASC | DESC ] ]
例:
“Persons” 表中的數(shù)據(jù)有
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
選出字段名” LastName”、” FirstName” 的數(shù)據(jù)
SELECT LastName,FirstName FROM Persons
|
返回結(jié)果:
LastName |
FirstName |
Hansen |
Ola |
Svendson |
Tove |
Pettersen |
Kari |
選出所有字段的數(shù)據(jù)
SELECT * FROM Persons
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
Where
用途:
被用來規(guī)定一種選擇查詢的標(biāo)準(zhǔn)
語法:
SELECT column FROM table WHERE column condition value
|
下面的操作符能被使用在WHERE中:
=,<>,>,<,>=,<=,BETWEEN,LIKE
注意: 在某些SQL的版本中不等號(hào)< >能被寫作為!=
解釋:
SELECT語句返回WHERE子句中條件為true的數(shù)據(jù)
例:
從” Persons”表中選出生活在” Sandnes” 的人
SELECT * FROM Persons WHERE City='Sandnes'
|
"Persons" 表中的數(shù)據(jù)有:
LastName |
FirstName |
Address |
City |
Year |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
1951 |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
1978 |
Svendson |
Stale |
Kaivn 18 |
Sandnes |
1980 |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
1960 |
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Year |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
1951 |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
1978 |
Svendson |
Stale |
Kaivn 18 |
Sandnes |
1980 |
And & Or
用途:
在WHERE子句中AND和OR被用來連接兩個(gè)或者更多的條件
解釋:
AND在結(jié)合兩個(gè)布爾表達(dá)式時(shí),只有在兩個(gè)表達(dá)式都為 TRUE 時(shí)才傳回 TRUE
OR在結(jié)合兩個(gè)布爾表達(dá)式時(shí),只要其中一個(gè)條件為 TRUE 時(shí),OR便傳回 TRUE
例:
"Persons" 表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Svendson |
Stephen |
Kaivn 18 |
Sandnes |
用AND運(yùn)算子來查找"Persons" 表中FirstName為”Tove”而且LastName為” Svendson”的數(shù)據(jù)
SELECT * FROM Persons
WHERE FirstName='Tove'
AND LastName='Svendson'
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
用OR運(yùn)算子來查找"Persons" 表中FirstName為”Tove”或者LastName為” Svendson”的數(shù)據(jù)
SELECT * FROM Persons
WHERE firstname='Tove'
OR lastname='Svendson'
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Svendson |
Stephen |
Kaivn 18 |
Sandnes |
你也能結(jié)合AND和OR (使用括號(hào)形成復(fù)雜的表達(dá)式),如:
SELECT * FROM Persons WHERE
(FirstName='Tove' OR FirstName='Stephen')
AND LastName='Svendson'
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Svendson |
Stephen |
Kaivn 18 |
Sandnes |
Between…And
用途:
指定需返回?cái)?shù)據(jù)的范圍
語法:
SELECT column_name FROM table_name
WHERE column_name
BETWEEN value1 AND value2
|
例:
“Persons”表中的原始數(shù)據(jù)
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Nordmann |
Anna |
Neset 18 |
Sandnes |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
用BETWEEN…AND返回LastName為從”Hansen”到”Pettersen”的數(shù)據(jù):
SELECT * FROM Persons WHERE LastName
BETWEEN 'Hansen' AND 'Pettersen'
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Nordmann |
Anna |
Neset 18 |
Sandnes |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
為了顯示指定范圍之外的數(shù)據(jù),也可以用NOT操作符:
SELECT * FROM Persons WHERE LastName
NOT BETWEEN 'Hansen' AND 'Pettersen'
|
返回結(jié)果:
LastName |
FirstName |
Address |
City |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Distinct
用途:
DISTINCT關(guān)鍵字被用作返回唯一的值
語法:
SELECT DISTINCT column-name(s) FROM table-name
|
解釋:
當(dāng)column-name(s)中存在重復(fù)的值時(shí),返回結(jié)果僅留下一個(gè)
例:
“Orders”表中的原始數(shù)據(jù)
Company |
OrderNumber |
Sega |
3412 |
W3Schools |
2312 |
Trio |
4678 |
W3Schools |
6798 |
用DISTINCT關(guān)鍵字返回Company字段中唯一的值:
SELECT DISTINCT Company FROM Orders
|
返回結(jié)果:
Company |
Sega |
W3Schools |
Trio |
Order by
用途:
指定結(jié)果集的排序
語法:
SELECT column-name(s) FROM table-name ORDER BY { order_by_expression [ ASC | DESC ] } |
解釋:
指定結(jié)果集的排序,可以按照ASC(遞增方式排序,從最低值到最高值)或者DESC(遞減方式排序,從最高值到最低值)的方式進(jìn)行排序,默認(rèn)的方式是ASC
例:
“Orders”表中的原始數(shù)據(jù):
Company |
OrderNumber |
Sega |
3412 |
ABC Shop |
5678 |
W3Schools |
2312 |
W3Schools |
6798 |
按照Company字段的升序方式返回結(jié)果集:
SELECT Company, OrderNumber FROM Orders
ORDER BY Company
|
返回結(jié)果:
Company |
OrderNumber |
ABC Shop |
5678 |
Sega |
3412 |
W3Schools |
6798 |
W3Schools |
2312 |
按照Company字段的降序方式返回結(jié)果集:
SELECT Company, OrderNumber FROM Orders
ORDER BY Company DESC
|
返回結(jié)果:
Company |
OrderNumber |
W3Schools |
6798 |
W3Schools |
2312 |
Sega |
3412 |
ABC Shop |
5678 |
Group by
用途:
對(duì)結(jié)果集進(jìn)行分組,常與匯總函數(shù)一起使用。
語法:
SELECT column,SUM(column) FROM table GROUP BY column
|
例:
“Sales”表中的原始數(shù)據(jù):
Company |
Amount |
W3Schools |
5500 |
IBM |
4500 |
W3Schools |
7100 |
按照Company字段進(jìn)行分組,求出每個(gè)Company的Amout的合計(jì):
SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company
|
返回結(jié)果:
Company |
SUM(Amount) |
W3Schools |
12600 |
IBM |
4500 |
Having
用途:
指定群組或匯總的搜尋條件。
語法:
SELECT column,SUM(column) FROM table
GROUP BY column
HAVING SUM(column) condition value
|
解釋:
HAVING 通常與 GROUP BY 子句同時(shí)使用。不使用 GROUP BY 時(shí),HAVING 則與 WHERE 子句功能相似。
例:
“Sales”表中的原始數(shù)據(jù):
Company |
Amount |
W3Schools |
5500 |
IBM |
4500 |
W3Schools |
7100 |
按照Company字段進(jìn)行分組,求出每個(gè)Company的Amout的合計(jì)在10000以上的數(shù)據(jù):
SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company HAVING SUM(Amount)>10000
|
返回結(jié)果:
Company |
SUM(Amount) |
W3Schools |
12600 |
Join
用途:
當(dāng)你要從兩個(gè)或者以上的表中選取結(jié)果集時(shí),你就會(huì)用到JOIN。
例:
“Employees”表中的數(shù)據(jù)如下,(其中ID為主鍵):
ID |
Name |
01 |
Hansen, Ola |
02 |
Svendson, Tove |
03 |
Svendson, Stephen |
04 |
Pettersen, Kari |
“Orders”表中的數(shù)據(jù)如下:
ID |
Product |
01 |
Printer |
03 |
Table |
03 |
Chair |
用Employees的ID和Orders的ID相關(guān)聯(lián)選取數(shù)據(jù):
SELECT Employees.Name, Orders.Product
FROM Employees, Orders
WHERE Employees.ID = Orders.ID
|
返回結(jié)果:
Name |
Product |
Hansen, Ola |
Printer |
Svendson, Stephen |
Table |
Svendson, Stephen |
Chair |
或者你也可以用JOIN關(guān)鍵字來完成上面的操作:
SELECT Employees.Name, Orders.Product
FROM Employees
INNER JOIN Orders
ON Employees.ID = Orders.ID
|
INNER JOIN的語法:
SELECT field1, field2, field3
FROM first_table
INNER JOIN second_table
ON first_table.keyfield = second_table.foreign_keyfield
|
解釋:
INNER JOIN返回的結(jié)果集是兩個(gè)表中所有相匹配的數(shù)據(jù)。
LEFT JOIN的語法:
SELECT field1, field2, field3
FROM first_table
LEFT JOIN second_table
ON first_table.keyfield = second_table.foreign_keyfield
|
用”Employees”表去左外聯(lián)結(jié)”Orders”表去找出相關(guān)數(shù)據(jù):
SELECT Employees.Name, Orders.Product
FROM Employees
LEFT JOIN Orders
ON Employees.ID = Orders.ID
|
返回結(jié)果:
Name |
Product |
Hansen, Ola |
Printer |
Svendson, Tove |
|
Svendson, Stephen |
Table |
Svendson, Stephen |
Chair |
Pettersen, Kari |
|
解釋:
LEFT JOIN返回”first_table”中所有的行盡管在” second_table”中沒有相匹配的數(shù)據(jù)。
RIGHT JOIN的語法:
SELECT field1, field2, field3
FROM first_table
RIGHT JOIN second_table
ON first_table.keyfield = second_table.foreign_keyfield
|
用”Employees”表去右外聯(lián)結(jié)”Orders”表去找出相關(guān)數(shù)據(jù):
SELECT Employees.Name, Orders.Product
FROM Employees
RIGHT JOIN Orders
ON Employees.ID = Orders.ID
|
返回結(jié)果:
Name |
Product |
Hansen, Ola |
Printer |
Svendson, Stephen |
Table |
Svendson, Stephen |
Chair |
解釋:
RIGHT JOIN返回” second_table”中所有的行盡管在”first_table”中沒有相匹配的數(shù)據(jù)。
Alias
用途:
可用在表、結(jié)果集或者列上,為它們?nèi)∫粋€(gè)邏輯名稱
語法:
給列取別名:
SELECT column AS column_alias FROM table
|
給表取別名:
SELECT column FROM table AS table_alias
|
例:
“Persons”表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
City |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
運(yùn)行下面的SQL:
SELECT LastName AS Family, FirstName AS Name
FROM Persons
|
返回結(jié)果:
Family |
Name |
Hansen |
Ola |
Svendson |
Tove |
Pettersen |
Kari |
運(yùn)行下面的SQL:
SELECT LastName, FirstName
FROM Persons AS Employees
|
返回結(jié)果:
Employees中的數(shù)據(jù)有:
LastName |
FirstName |
Hansen |
Ola |
Svendson |
Tove |
Pettersen |
Kari |
Insert Into
用途:
在表中插入新行
語法:
插入一行數(shù)據(jù)
INSERT INTO table_name
VALUES (value1, value2,....)
|
插入一行數(shù)據(jù)在指定的字段上
INSERT INTO table_name (column1, column2,...)
VALUES (value1, value2,....)
|
例:
“Persons”表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
City |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
運(yùn)行下面的SQL插入一行數(shù)據(jù):
INSERT INTO Persons
VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes')
|
插入后”Persons”表中的數(shù)據(jù)為:
LastName |
FirstName |
Address |
City |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
Hetland |
Camilla |
Hagabakka 24 |
Sandnes |
運(yùn)行下面的SQL插入一行數(shù)據(jù)在指定的字段上:
INSERT INTO Persons (LastName, Address)
VALUES ('Rasmussen', 'Storgt 67')
|
插入后”Persons”表中的數(shù)據(jù)為:
LastName |
FirstName |
Address |
City |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
Hetland |
Camilla |
Hagabakka 24 |
Sandnes |
Rasmussen |
|
Storgt 67 |
|
Update
用途:
更新表中原有數(shù)據(jù)
語法:
UPDATE table_name SET column_name = new_value
WHERE column_name = some_value
|
例:
“Person”表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
City |
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
Rasmussen |
|
Storgt 67 |
|
運(yùn)行下面的SQL將Person表中LastName字段為”Rasmussen”的FirstName更新為”Nina”:
UPDATE Person SET FirstName = 'Nina'
WHERE LastName = 'Rasmussen'
|
更新后”Person”表中的數(shù)據(jù)為:
LastName |
FirstName |
Address |
City |
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
Rasmussen |
Nina |
Storgt 67 |
|
同樣的,用UPDATE語句也可以同時(shí)更新多個(gè)字段:
UPDATE Person
SET Address = 'Stien 12', City = 'Stavanger'
WHERE LastName = 'Rasmussen'
|
更新后”Person”表中的數(shù)據(jù)為:
LastName |
FirstName |
Address |
City |
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
Rasmussen |
Nina |
Stien 12 |
Stavanger |
Delete
用途:
刪除表中的數(shù)據(jù)
語法:
DELETE FROM table_name WHERE column_name = some_value
|
例:
“Person”表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
City |
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
Rasmussen |
Nina |
Stien 12 |
Stavanger |
刪除Person表中LastName為”Rasmussen”的數(shù)據(jù):
DELETE FROM Person WHERE LastName = 'Rasmussen'
|
執(zhí)行刪除語句后”Person”表中的數(shù)據(jù)為:
LastName |
FirstName |
Address |
City |
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
Create Table
用途:
建立新的資料表。
語法:
CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
.......
)
|
例:
創(chuàng)建一張叫“Person”的表,該表有4個(gè)字段"LastName", "FirstName", "Address", "Age":
CREATE TABLE Person
(
LastName varchar,
FirstName varchar,
Address varchar,
Age int
)
|
如果想指定字段的最大存儲(chǔ)長度,你可以這樣:
CREATE TABLE Person
(
LastName varchar(30),
FirstName varchar(30),
Address varchar(120),
Age int(3)
)
|
下表中列出了在SQL的一些數(shù)據(jù)類型:
Data Type |
Description |
integer(size) |
Hold integers only. The maximum number of digits are specified in parenthesis. |
decimal(size,d) |
Hold numbers with fractions. The maximum number of digits are specified in "size". The maximum number of digits to the right of the decimal is specified in "d". |
char(size) |
Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis. |
varchar(size) |
Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis. |
date(yyyymmdd) |
Holds a date |
Alter Table
用途:
在已經(jīng)存在的表中增加后者移除字段
語法:
ALTER TABLE table_name
ADD column_name datatype
ALTER TABLE table_name
DROP COLUMN column_name
|
注意:某些數(shù)據(jù)庫管理系統(tǒng)不允許移除表中的字段
例:
“Person”表中的原始數(shù)據(jù):
LastName |
FirstName |
Address |
Pettersen |
Kari |
Storgt 20 |
在Person表中增加一個(gè)名為City的字段:
ALTER TABLE Person ADD City varchar(30)
|
增加后表中數(shù)據(jù)如下:
LastName |
FirstName |
Address |
City |
Pettersen |
Kari |
Storgt 20 |
|
移除Person表中原有的Address字段:
ALTER TABLE Person DROP COLUMN Address
|
移除后表中數(shù)據(jù)如下:
LastName |
FirstName |
City |
Pettersen |
Kari |
|
Drop Table
用途:
在數(shù)據(jù)庫中移除一個(gè)數(shù)據(jù)表定義及該數(shù)據(jù)表中的所有資料、索引、觸發(fā)程序、條件約束及權(quán)限指定。
語法:
DROP TABLE table_name
|
Create Database
用途:
建立新的數(shù)據(jù)庫.
語法:
CREATE DATABASE database_name
|
Drop Database
用途:
移除原有的數(shù)據(jù)庫
語法:
DROP DATABASE database_name
|
聚集函數(shù)
count
用途:
傳回選取的結(jié)果集中行的數(shù)目。
語法:
SELECT COUNT(column_name) FROM table_name
|
例:
“Persons”表中原始數(shù)據(jù)如下:
Name |
Age |
Hansen, Ola |
34 |
Svendson, Tove |
45 |
Pettersen, Kari |
19 |
選取記錄總數(shù):
SELECT COUNT(Name) FROM Persons
|
執(zhí)行結(jié)果:
3
|
sum
用途:
以表達(dá)式傳回所有值的總和,或僅 DISTINCT 值。SUM 僅可用于數(shù)值資料行。已忽略 Null 值。
語法:
SELECT SUM(column_name) FROM table_name
|
例:
“Persons”表中原始數(shù)據(jù)如下:
Name |
Age |
Hansen, Ola |
34 |
Svendson, Tove |
45 |
Pettersen, Kari |
19 |
選取”Persons”表中所有人的年齡總和:
SELECT SUM(Age) FROM Persons
|
執(zhí)行結(jié)果:
98
|
選取”Persons”表中年齡超過20歲的人的年齡總和:
SELECT SUM(Age) FROM Persons WHERE Age>20
|
執(zhí)行結(jié)果:
79
|
avg
用途:
傳回選取的結(jié)果集中值的平均值。已忽略 Null 值。
語法:
SELECT AVG(column_name) FROM table_name
|
例:
“Persons”表中原始數(shù)據(jù)如下:
Name |
Age |
Hansen, Ola |
34 |
Svendson, Tove |
45 |
Pettersen, Kari |
19 |
選取”Persons”表中所有人的平均年齡:
SELECT AVG(Age) FROM Persons
|
執(zhí)行結(jié)果:
32.67
|
選取”Persons”表中年齡超過20歲的人的平均年齡:
SELECT AVG(Age) FROM Persons WHERE Age>20
|
執(zhí)行結(jié)果:
39.5
|
max
用途:
傳回選取的結(jié)果集中值的最大值。已忽略 Null 值。
語法:
SELECT MAX(column_name) FROM table_name
|
例:
“Persons”表中原始數(shù)據(jù)如下:
Name |
Age |
Hansen, Ola |
34 |
Svendson, Tove |
45 |
Pettersen, Kari |
19 |
選取”Persons”表中的最大年齡:
SELECT MAX(Age) FROM Persons
|
執(zhí)行結(jié)果:
45
|
min
用途:
傳回選取的結(jié)果集中值的最小值。已忽略 Null 值。
語法:
SELECT MIN(column_name) FROM table_name
|
例:
“Persons”表中原始數(shù)據(jù)如下:
Name |
Age |
Hansen, Ola |
34 |
Svendson, Tove |
45 |
Pettersen, Kari |
19 |
選取”Persons”表中的最小年齡:
SELECT MIN(Age) FROM Persons
|
執(zhí)行結(jié)果:
19
|
算術(shù)函數(shù)
abs
用途:
傳回指定數(shù)值表達(dá)式 (Numeric Expression) 的絕對(duì)正值。
語法:
ABS(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
ceil
用途:
傳回大于等于給定數(shù)值表達(dá)式的最小整數(shù)。
語法:
CEIL(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
floor
用途:
傳回小于或等于給定數(shù)值表達(dá)式的最大整數(shù)。
語法:
FLOOR(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
cos
用途:
在指定表達(dá)式中傳回指定角度 (以弳度為單位) 的三角余弦值的數(shù)學(xué)函數(shù)。
語法:
COS(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
-0.599465
|
cosh
用途:
傳回以弧度為單位的角度值,其余弦為指定的 float 表達(dá)式,也稱為反余弦。
語法:
COSH(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
3.14159
|
sin
用途:
以近似的數(shù)值 (float) 表達(dá)式傳回給定角度 (以弧度) 之三角正弦函數(shù) (Trigonometric Sine)。
語法:
SIN(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
sinh
用途:
傳回以弳度為單位的角度,其正弦為指定的 float 表達(dá)式 (也稱為反正弦)。
語法:
SINH(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
tan
用途:
傳回輸入表達(dá)式的正切函數(shù)。
語法:
TAN(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
tanh
用途:
傳回以弳度為單位的角度,其正切為指定的 float 表達(dá)式 (也稱為反正切)。
語法:
TANH(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
exp
用途:
傳回給定的 float 表達(dá)式的指數(shù) (Exponential) 值。
語法:
EXP(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
log
用途:
傳回給定的 float 表達(dá)式之自然對(duì)數(shù)。
語法:
LOG(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
power
用途:
傳回給定表達(dá)式指定乘冪的值。
語法:
POWER(numeric_expression,v) |
例:
|
執(zhí)行結(jié)果:
|
sign
用途:
傳回給定的表達(dá)式之正 (+1)、零 (0) 或負(fù) (-1) 號(hào)。
語法:
SIGN(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
sqrt
用途:
傳回給定表達(dá)式的平方。
語法:
SQRT(numeric_expression) |
例:
|
執(zhí)行結(jié)果:
|
地震讓大伙知道:居安思危,才是生存之道。
