SQL is an ANSI standard. Each database vendor develops its own database and language according to this standard. SQL Server is called T-SQL. Oracle's called PL/SQL.
A little summary of some of the commonly used T-SQL some things, think of where to write, the great God do not spray.
Function
1. Mathematical Functions
Min (COLUMN): Minimum value-aggregate function;
Max (COLUMN): maximum-aggregate function;
AVG (COLUMN): Average--aggregate function;
SUM (COLUMN): Sum--aggregate function;
COUNT (COLUMN): Total-aggregate function;
ABS (X): absolute value;
SQRT (X): square root;
POWER (x, y): prescribe;
EXP (X): exponent;
Log (x, y): logarithmic;
Sign (X): Find the symbol;
RAND ([0]): Returns the random float value between 0~1, automatically outputs random values when the parameter is empty, and returns the same value as the same parameter;
Floor (x): Returns the largest integer less than or equal to the X value;
CEILING (x): Returns the smallest integer greater than or equal to the x value;
ROUND (x,length): Rounding function, length is positive, then the X decimal place rounding, length is negative, the X decimal points to the left of the length of the rounding, if length is both negative and its absolute value is greater than the number of x integer part, the function value is 0;
2. String Functions
Lower (XXX): Converts a string to lowercase;
UPPER (XXX): Converts a string to lowercase;
LTRIM (XXX): go short lattice;
RTRIM (XXX): Go to the right space;
Left (Xxx,y): Returns the specified number of characters from the beginning of the total string;
Right (Xxx,y): Returns the specified number of characters from the beginning of the string;
LEN (XXX): Returns the number of string characters;
Datalength (XXX): Returns the length of bytes passed;
SUBSTRING (XXX, Y, Z): Returns a string of Z from the left Y of the string
Replace (XXX,YYY,ZZZ): Replaces all YYY characters appearing in XXX with ZZZ;
STUFF (XXX, Y, Z, MMM): delete xxx Specify position Y start specifying length Z string and insert MMM at specified position;
REVERSE (XXX): Reverses the order of the characters of the specified string;
3. Conversion Functions
Cast (xxx as DATATYPE): convert XXX to other data types;
Convert (datatypeb,xxx): Convert XXX to Datatypeb
4. Conversion Functions
GETDATE (): Gets the current time;
--Get the current year date YY representative years, MM for the month, DD on behalf of the day, HH for the time, the SS represents the second
Year YY 1753--9999
Quarter QQ 1--4
month mm 1--12
Day of the year dy 1--366
Day DD 1--31
Week wk 1--53
Weekday DW 1--7 (Sunday--saturday)
Hour HH 0--23
Minute Mi 0--59
Second SS 0--59
Milisecond Ms 0--999
DATEPART (Qq,getdate ()): Returns the current QQ (quarter-integer);
Datename (Qq,getdate ()): Returns the current QQ (quarter-character);
DATEDIFF (DD, ' 2011-7-7 ', GETDATE ()): To obtain two periods of time apart from the years yy, a few months mm, a few days DD;
DATEADD (Mm,-2,getdate ()): Add or subtract month and day from the current time
T-SQL Summary