Aggregate Functions
COS Select supports the following aggregate functions:
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| | 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. |
| | |
| | The return value type is the same as that of the input parameter |
| | The return value type is the same as that of the input parameter |
| 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. |
Condition Functions
COS Select supports the following condition functions:
COALESCE
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.
Syntax
COALESCE ( expression, expression, ... )
Note:
Values, arrays, or nested functions of INT, String, and Float types can be passed in for the expression parameter.
Sample
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
NULLIF
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.
Syntax
NULLIF ( expression1, expression2 )
Note:
Values, arrays, or nested functions of INT, String, and Float types can be passed in for the expression parameter.
Sample
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
Conversion Functions
COS Select supports the following conversion functions:
CAST
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.
Syntax
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. Sample
CAST('2007-04-05T14:30Z' AS TIMESTAMP)
CAST(0.456 AS FLOAT)
Date Functions
COS Select supports the following date functions:
DATE_ADD
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.
Syntax
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.
Sample
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
DATE_DIFF
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.
Syntax
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.
Sample
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.
Syntax
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.
Sample
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
TO_STRING
The TO_STRING function converts a timestamp to a string of time in the specified format.
Syntax
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.
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| | |
| | |
| Year expressed by 4 digits. If there are less than 4 digits, 0 will be automatically added | |
| | |
| Month expressed by 2 digits. If there are less than 2 digits, 0 will be automatically added | |
| English abbreviation of a month | |
| Full English name of a month | |
| | J (not applicable to the to_timestamp function) |
| | |
| Day expressed by 2 digits (1-31) | |
| Symbol for morning or afternoon (AM/PM) | |
| | |
| Hour expressed by 2 digits in 12-hour time | |
| | |
| Hour expressed by 2 digits in 24-hour time | |
| | |
| Minute expressed by 2 digits in 24-hour time | |
| | |
| Second expressed by 2 digits in 24-hour time | |
| Decimal part of the second (accuracy: 0.1; value range: 0.0 - 0.9) | |
| Decimal part of the second (accuracy: 0.01; value range: 0.00 - 0.99) | |
| Decimal part of the second (accuracy: 0.001; value range: 0.000 - 0.999) | |
| | |
| Decimal part of the second (accuracy: 0.000000001; value range: 0.000000000 - 0.999999999) | |
| | |
| Hour-level offset. If the offset is 0, then this will be "Z" | |
| Hour- or minute-level offset. If the offset is 0, then this will be "Z" | |
| Hour- or minute-level offset. If the offset is 0, then this will be "Z" | |
| | |
| Hour- or minute-level offset | |
| Hour- or minute-level offset | |
Sample
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"
TO_TIMESTAMP
The TO_TIMESTAMP function converts a string of time to a timestamp.
Syntax
Note:
The string parameter represents the input time string.
Sample
TO_TIMESTAMP('2007T') -- `2007T`
TO_TIMESTAMP('2007-02-23T12:14:33.079-08:00') -- `2007-02-23T12:14:33.079-08:00`
UTCNOW
The UTCNOW function returns the current timestamp in UTC.
Syntax
Sample
UTCNOW() -- 2019-01-01T14:23:12.123Z
String Functions
COS Select supports the following string functions:
CHAR_LENGTH, CHARACTER_LENGTH
Both CHAR_LENGTH and CHARACTER_LENGTH can compute the number of characters in a string, and they have the same semantics.
Syntax
Note:
The string parameter specifies the string for character counting
Sample
CHAR_LENGTH('null') -- 4
CHAR_LENGTH('tencent') -- 7
LOWER
The LOWER function converts all uppercase letters in the specified string to lowercase letters, with all non-uppercase letters left unchanged.
Syntax
Note:
The string parameter specifies the string for which to convert uppercase letters to lowercase letters.
Sample
LOWER('TENcent') -- 'tencent'
SUBSTRING
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 be greater than 1, the SUBSTRING function will automatically switch it to 1.
Syntax
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.
Sample
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"
TRIM
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.
Syntax
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 the string parameter.
Sample
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'
UPPER
The UPPER function converts all lowercase letters to uppercase letters with non-lowercase letters left unchanged.
Syntax
Note:
The string parameter specifies the string to be converted to uppercase letters.
Sample
UPPER('tenCENT') -- 'TENCENT'
