COS Select supports the following aggregate functions:
Function Name | Parameter Type | Return Type |
---|---|---|
AVG(expression) | INT, FLOAT, and DECIMAL | DECIMAL will be returned if the input parameter is of integer type, and FLOAT if float type. The same type as the input parameter will be returned in all other cases. |
COUNT | - | INT |
MAX(expression) | INT and DECIMAL | The return value type is the same as that of the input parameter |
MIN(expression) | INT and DECIMAL | The return value type is the same as that of the input parameter |
SUM(expression) | INT, FLOAT, DOUBLE, and DECIMAL | INT will be returned if the input parameter is of integer type, and FLOAT if float type. The same type as the input parameter will be returned in all other cases. |
COS Select supports the following condition functions:
The COALESCE function determines the input parameters in sequence and returns the first non-null parameter value. If the input parameters do not include a non-null parameter, the function will return a null value.
COALESCE ( expression, expression, ... )
Note:
Values, arrays, or nested functions of INT, String, and Float types can be passed in for the
expression
parameter.
COALESCE(1) -- 1
COALESCE(1, null) -- 1
COALESCE(null, null, 1) -- 1
COALESCE(missing, 1) -- 1
COALESCE(null, 'string') -- 'string'
COALESCE(null) -- null
COALESCE(null, null) -- null
COALESCE(missing) -- null
COALESCE(missing, missing) -- null
The NULLIF function determines the difference between two parameters passed in. If the two parameters have the same value, NULL will be returned; otherwise, the value of the first parameter passed in will be returned.
NULLIF ( expression1, expression2 )
Note:
Values, arrays, or nested functions of INT, String, and Float types can be passed in for the
expression
parameter.
NULLIF(1, 2) -- 1
NULLIF(1, '1') -- 1
NULLIF(1, NULL) -- 1
NULLIF(1, 1) -- null
NULLIF(1.0, 1) -- null
NULLIF(missing, null) -- null
NULLIF(missing, missing) -- null
NULLIF([1], [1]) -- null
NULLIF(NULL, 1) -- null
NULLIF(null, null) -- null
COS Select supports the following conversion functions:
The CAST function converts one instance to another instance. The instance can be either a value or a function that can be calculated to a certain value.
CAST ( expression AS data_type )
Note:
- The
expression
parameter can be a value, an array, an operator, or an SQL function that can be calculated to a certain value.- The
data_type
parameter is the data type after conversion, such as INT. For the data types currently supported by COS Select, see Data Types.
CAST('2007-04-05T14:30Z' AS TIMESTAMP)
CAST(0.456 AS FLOAT)
COS Select supports the following date functions:
The DATE_ADD function adds a specified time interval to a part (year, month, day, hour, minute, or second) of a specific timestamp and returns a new timestamp.
DATE_ADD( date_part, quantity, timestamp )
Note:
- The
date_part
parameter specifies the part of the timestamp to be modified, which can be year, month, day, hour, minute, or second.- The
quantity
parameter represents the value to be added, which must be a positive integer.- The
timestamp
parameter represents the timestamp to be modified.
DATE_ADD(year, 5, `2010-01-01T`) -- 2015-01-01
DATE_ADD(month, 1, `2010T`) -- 2010-02T
DATE_ADD(month, 13, `2010T`) -- 2011-02T
DATE_ADD(hour, 1, `2017T`) -- 2017-01-01T01:00-00:00
DATE_ADD(hour, 1, `2017-01-02T03:04Z`) -- 2017-01-02T04:04Z
DATE_ADD(minute, 1, `2017-01-02T03:04:05.006Z`) -- 2017-01-02T03:05:05.006Z
DATE_ADD(second, 1, `2017-01-02T03:04:05.006Z`) -- 2017-01-02T03:04:06.006Z
The DATE_DIFF function compares two valid timestamps and returns the difference between them, which can be displayed in the specified unit of time. If the date_part
value of timestamp1 is greater than that of timestamp2, a positive number will be returned; otherwise, a negative number will be returned.
DATE_DIFF( date_part, timestamp1, timestamp2 )
Note:
- The
date_part
parameter specifies the unit of time which the two timestamps are compared in and can be year, month, day, hour, minute, or second.- The
timestamp1
parameter is the first input timestamp.- The
timestamp2
parameter is the second input timestamp.
DATE_DIFF(year, `2010-01-01T`, `2011-01-01T`) -- 1
DATE_DIFF(year, `2010T`, `2010-05T`) -- 4
DATE_DIFF(month, `2010T`, `2011T`) -- 12
DATE_DIFF(month, `2011T`, `2010T`) -- -12
DATE_DIFF(day, `2010-01-01T23:00T`, `2010-01-02T01:00T`) -- 0
The EXTRACT function extracts a value in the specified unit of time from a given timestamp.
EXTRACT( date_part FROM timestamp )
Note:
- The parameter
date_part
specifies the unit of time to be extracted, which can be year, month, day, hour, minute, or second.- The
timestamp
parameter represents the input timestamp.
EXTRACT(YEAR FROM `2010-01-01T`) -- 2010
EXTRACT(MONTH FROM `2010T`) -- 1
EXTRACT(MONTH FROM `2010-10T`) -- 10
EXTRACT(HOUR FROM `2017-01-02T03:04:05+07:08`) -- 3
EXTRACT(MINUTE FROM `2017-01-02T03:04:05+07:08`) -- 4
EXTRACT(TIMEZONE_HOUR FROM `2017-01-02T03:04:05+07:08`) -- 7
EXTRACT(TIMEZONE_MINUTE FROM `2017-01-02T03:04:05+07:08`) -- 8
The TO_STRING function converts a timestamp to a string of time in the specified format.
TO_STRING ( timestamp time_format_pattern )
Note:
- The
timestamp
parameter specifies the timestamp to be converted.- The
time_format_pattern
parameter specifies the time format.
Format | Description | Sample |
---|---|---|
yy | 2-digit year | 98 |
y | 4-digit year | 1998 |
yyyy | Year expressed by 4 digits. If there are less than 4 digits, 0 will be automatically added | 0199 |
M | Month | 1 |
MM | Month expressed by 2 digits. If there are less than 2 digits, 0 will be automatically added | 01 |
MMM | English abbreviation of a month | Jan |
MMMM | Full English name of a month | January |
MMMMM | Initial of a month | J (not applicable to the to_timestamp function) |
d | Day (1-31) in a month | 1 |
dd | Day expressed by 2 digits (1-31) | 01 |
a | Symbol for morning or afternoon (AM/PM) | AM |
h | Hour in 12-hour time | 1 |
hh | Hour expressed by 2 digits in 12-hour time | 01 |
H | Hour in 24-hour time | 1 |
HH | Hour expressed by 2 digits in 24-hour time | 01 |
m | Minute (00-59) | 1 |
mm | Minute expressed by 2 digits in 24-hour time | 01 |
s | Second (00-59) | 1 |
ss | Second expressed by 2 digits in 24-hour time | 01 |
S | Decimal part of the second (accuracy: 0.1; value range: 0.0 - 0.9) | 0 |
SS | Decimal part of the second (accuracy: 0.01; value range: 0.00 - 0.99) | 6 |
SSS | Decimal part of the second (accuracy: 0.001; value range: 0.000 - 0.999) | 60 |
... | ... | ... |
SSSSSSSSS | Decimal part of the second (accuracy: 0.000000001; value range: 0.000000000 - 0.999999999) | 60000000 |
n | Nanosecond | 60000000 |
X | Hour-level offset. If the offset is 0, then this will be "Z" | +01 or Z |
XX or XXXX | Hour- or minute-level offset. If the offset is 0, then this will be "Z" | +0100 or Z |
xxx or xxxxx | Hour- or minute-level offset. If the offset is 0, then this will be "Z" | +01:00 or Z |
x | Hour-level offset | 1 |
xx or xxxx | Hour- or minute-level offset | 0100 |
xxx or xxxxx | Hour- or minute-level offset | 01:00 |
TO_STRING(`1998-07-20T20:18Z`, 'MMMM d, y') -- "July 20, 1998"
TO_STRING(`1998-07-20T20:18Z`, 'MMM d, yyyy') -- "Jul 20, 1998"
TO_STRING(`1998-07-20T20:18Z`, 'M-d-yy') -- "7-20-69"
TO_STRING(`1998-07-20T20:18Z`, 'MM-d-y') -- "07-20-1998"
TO_STRING(`1998-07-20T20:18Z`, 'MMMM d, y h:m a') -- "July 20, 1998 8:18 PM"
TO_STRING(`1998-07-20T20:18Z`, 'y-MM-dd''T''H:m:ssX') -- "1998-07-20T20:18:00Z"
TO_STRING(`1998-07-20T20:18+08:00Z`, 'y-MM-dd''T''H:m:ssX') -- "1998-07-20T20:18:00Z"
TO_STRING(`1998-07-20T20:18+08:00`, 'y-MM-dd''T''H:m:ssXXXX') -- "1998-07-20T20:18:00+0800"
TO_STRING(`1998-07-20T20:18+08:00`, 'y-MM-dd''T''H:m:ssXXXXX') -- "1998-07-20T20:18:00+08:00"
The TO_TIMESTAMP function converts a string of time to a timestamp.
TO_TIMESTAMP ( string )
Note:
The
string
parameter represents the input time string.
TO_TIMESTAMP('2007T') -- `2007T`
TO_TIMESTAMP('2007-02-23T12:14:33.079-08:00') -- `2007-02-23T12:14:33.079-08:00`
The UTCNOW function returns the current timestamp in UTC.
UTCNOW()
UTCNOW() -- 2019-01-01T14:23:12.123Z
COS Select supports the following string functions:
Both CHAR_LENGTH and CHARACTER_LENGTH can compute the number of characters in a string, and they have the same semantics.
CHAR_LENGTH ( string )
Note:
The
string
parameter specifies the string for character counting
CHAR_LENGTH('null') -- 4
CHAR_LENGTH('tencent') -- 7
The LOWER function converts all uppercase letters in the specified string to lowercase letters, with all non-uppercase letters left unchanged.
LOWER ( string )
Note:
The
string
parameter specifies the string for which to convert uppercase letters to lowercase letters.
LOWER('TENcent') -- 'tencent'
The SUBSTRING function returns a substring of a string. You can specify an index from which the SUBSTRING function will extract the remainder of the original string based on the length of the specified substring and return the result.
Note:
If the input string contains only 1 character, and the index is set to greater than 1, the SUBSTRING function will automatically switch it to 1.
SUBSTRING( string FROM start [ FOR length ] )
Note:
- The
string
parameter specifies the string from which to extract a substring.- The
start
parameter represents an index value of the string as the starting position for extraction.- The
length
parameter specifies the length of the substring. If the length of the substring is not specified, the remainder of the string will be extracted.
SUBSTRING("123456789", 0) -- "123456789"
SUBSTRING("123456789", 1) -- "123456789"
SUBSTRING("123456789", 2) -- "23456789"
SUBSTRING("123456789", -4) -- "123456789"
SUBSTRING("123456789", 0, 999) -- "123456789"
SUBSTRING("123456789", 1, 5) -- "12345"
The TRIM function deletes all characters before the first character or after the last character of the specified string. " " is the default character to be deleted.
TRIM ( [[LEADING | TRAILING | BOTH remove_chars] FROM] string )
Note:
- The
string
parameter specifies the string to be manipulated.- The
LEADING | TRAILING | BOTH
parameter specifies the extra characters to be deleted, which can be before the string (LEADING), after the string (TRAILING), or both (BOTH).- The
remove_chars
parameter specifies the type of extra characters to be deleted. It can be a string containing more than one characters. The TRIM function will delete all extra characters of the corresponding type that are identified by the TRIM function before or after thestring
parameter.
TRIM(' foobar ') -- 'foobar'
TRIM(' \tfoobar\t ') -- '\tfoobar\t'
TRIM(LEADING FROM ' foobar ') -- 'foobar'
TRIM(TRAILING FROM ' foobar ') -- 'foobar'
TRIM(BOTH FROM ' foobar ') -- 'foobar'
TRIM(BOTH '12' FROM '1112211foobar22211122') -- 'foobar'
The UPPER function converts all lowercase letters to uppercase letters with non-lowercase letters left unchanged.
UPPER ( string )
Note:
The
string
parameter specifies the string to be converted to uppercase letters.
UPPER('tenCENT') -- 'TENCENT'
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