SQL如何获取最大间隔天数

Question

我需要寻找每个客户的所有日期上连续的订单中间隔最长的两笔。
现在有一组叫Orders的表格。包含如下内容：

+-------+------------+----------+
|OrderID|  OrderDate |CustomerID|
+-------+------------+----------+
|  101  | 2021-01-01 |     1    |
|  102  | 2021-01-10 |     1    |
|  103  | 2021-01-30 |     1    |
|  104  | 2020-11-01 |     2    |
|  105  | 2021-01-01 |     2    |
|  106  | 2021-01-22 |     2    |
|  107  | 2020-05-10 |     3    |
|  108  | 2020-07-10 |     3    |
|  109  | 2021-01-10 |     3    |
|  110  | 2021-01-13 |     4    |
|  ...  | .......... |   ....   |
+-------+------------+----------+

其中OrderID是订单编号，OrderDate是订单日期，CustomerID是客户。所有符合条件的CustomerID至少得有2个OrderID。所有不满足条件的用户不应该出现在最终结果里。

以上表格仅是参考。无法确定OrderDate和CustomerID的顺序。其实OrderID没有用，主要是关于OrderDate跟CustomerID。

其中包含4个客户（CustomerID），即 1，2，3，4。其中有3个跟1有关的OrderID，3个跟2有关的OrderID，3个跟3有关的OrderID，1个跟1有关的OrderID。因为客户4只有一笔订单，所以客户4不存在最大间隔时长，所以结果里的CustomerID不应该含有4。

关于连续的订单，它的意思是像101（2021-01-01）跟102（2021-01-10）是连续的，102（2021-01-10）跟103（2021-01-30）是连续的，但101跟103不是连续的，因为102的时间是在101跟103中间。所以最大日期减去最小日期得出的结果是不正确的。

此情况下，正确的结果应该是：

客户（CustomerID）	最大时长（天）	具体订单（OrderID）
1	20（天）	订单号102（2021-01-10）订单号102（2021-01-30）
2	61（天）	订单号105（2021-01-10）订单号104（2021-01-30）
3	122（天）	订单号108（2020-07-10）订单号109（2021-01-10）

上述表格返回的结果应该是：

+----------+----------+
|CustomerID|  NumDays |
+----------+----------+
|     1    |    20    |
|     2    |    61    |
|     3    |   122    |
+----------+----------+

有很多东西是不能用的。比如说lag，limit，over。这是我看最常用的几种做法。但是它们一概都不能用。

我说实话对于这个问题完全不知道该怎么入手，希望能有人指导。

补充：所有不能使用的都在这个txt文件里了：forbidden.txt。很抱歉之前没有附上。

补充：所有不能用的如下：

不能使用的（forbidden.txt中的全部内容）
ABORT
ABS
ABSENT
ABSOLUTE
ACCESS
ACCORDING
ACOS
ACTION
ADA
ADD
ADMIN
AFTER
AGGREGATE
ALLOCATE
ALSO
ALTER
ALWAYS
ANALYSE
ANALYZE
ARRAY
ARRAY_AGG
ARRAY_MAX_CARDINALITY
ASENSITIVE
ASIN
ASSERTION
ASSIGNMENT
ASYMMETRIC
ATAN
ATOMIC
ATTACH
AUTHORIZATION
BACKWARD
BASE64
BEFORE
BEGIN
BEGIN_FRAME
BEGIN_PARTITION
BERNOULLI
BETWEEN
BIGINT
BINARY
BIT
BIT_LENGTH
BLOB
BLOCKED
BOM
BOTH
BREADTH
CACHE
CALL
CALLED
CARDINALITY
CASCADE
CASCADED
CATALOG
CATALOG_NAME
CEIL
CEILING
CHAIN
CHAINING
CHARACTERISTICS
CHARACTERS
CHARACTER_LENGTH
CHARACTER_SET_CATALOG
CHARACTER_SET_NAME
CHARACTER_SET_SCHEMA
CHAR_LENGTH
CHECK
CHECKPOINT
CLASS
CLASSIFIER
CLASS_ORIGIN
CLOB
CLOSE
CLUSTER
COALESCE
COBOL
COLLATE
COLLATION
COLLATION_CATALOG
COLLATION_NAME
COLLATION_SCHEMA
COLLECT
COMMAND_FUNCTION
COMMAND_FUNCTION_CODE
COMMENT
COMMENTS
COMMIT
COMMITTED
CONCURRENTLY
CONDITION
CONDITIONAL
CONDITION_NUMBER
CONFIGURATION
CONFLICT
CONNECT
CONNECTION
CONNECTION_NAME
CONSTRAINT
CONSTRAINTS
CONSTRAINT_CATALOG
CONSTRAINT_NAME
CONSTRAINT_SCHEMA
CONSTRUCTOR
CONTAINS
CONTENT
CONTINUE
CONTROL
CONVERSION
CONVERT
COPY
CORR
CORRESPONDING
COS
COSH
COST
COVAR_POP
COVAR_SAMP
CREATE
CROSS
CSV
CUBE
CUME_DIST
CURRENT
CURRENT_CATALOG
CURRENT_DATE
CURRENT_DEFAULT_TRANSFORM_GROUP
CURRENT_PATH
CURRENT_ROLE
CURRENT_ROW
CURRENT_SCHEMA
CURRENT_TIME
CURRENT_TIMESTAMP
CURRENT_TRANSFORM_GROUP_FOR_TYPE
CURRENT_USER
CURSOR
CURSOR_NAME
CYCLE
DATA
DATABASE
DATALINK
DATETIME_INTERVAL_CODE
DATETIME_INTERVAL_PRECISION
DAY
DEALLOCATE
DEC
DECFLOAT
DECLARE
DEFAULT
DEFAULTS
DEFERRABLE
DEFERRED
DEFINE
DEFINED
DEFINER
DELETE
DELIMITER
DELIMITERS
DENSE_RANK
DEPENDS
DEPTH
DEREF
DERIVED
DESCRIBE
DESCRIPTOR
DETACH
DETERMINISTIC
DIAGNOSTICS
DICTIONARY
DISABLE
DISCARD
DISCONNECT
DISPATCH
DLNEWCOPY
DLPREVIOUSCOPY
DLURLCOMPLETE
DLURLCOMPLETEONLY
DLURLCOMPLETEWRITE
DLURLPATH
DLURLPATHONLY
DLURLPATHWRITE
DLURLSCHEME
DLURLSERVER
DLVALUE
DO
DOCUMENT
DOMAIN
DOUBLE
DROP
DYNAMIC
DYNAMIC_FUNCTION
DYNAMIC_FUNCTION_CODE
EACH
ELEMENT
EMPTY
ENABLE
ENCODING
ENCRYPTED
END_FRAME
END_PARTITION
ENFORCED
ENUM
EQUALS
ERROR
ESCAPE
EVENT
EVERY
EXCEPTION
EXCLUDE
EXCLUDING
EXCLUSIVE
EXEC
EXECUTE
EXP
EXPLAIN
EXPRESSION
EXTENSION
EXTERNAL
EXTRACT
FAMILY
FETCH
FILE
FILTER
FINAL
FINISH
FIRST
FIRST_VALUE
FLAG
FLOAT
FLOOR
FOLLOWING
FOR
FORCE
FOREIGN
FORMAT
FORTRAN
FORWARD
FOUND
FRAME_ROW
FREE
FREEZE
FULFILL
FULL
FUNCTION
FUNCTIONS
FUSION
GENERAL
GENERATED
GET
GLOBAL
GO
GOTO
GRANT
GRANTED
GREATEST
GROUPING
GROUPS
HANDLER
HEADER
HEX
HIERARCHY
HOLD
HOUR
IDENTITY
IF
IGNORE
ILIKE
IMMEDIATE
IMMEDIATELY
IMMUTABLE
IMPLEMENTATION
IMPLICIT
IMPORT
INCLUDE
INCLUDING
INCREMENT
INDENT
INDEX
INDEXES
INDICATOR
INHERIT
INHERITS
INITIAL
INITIALLY
INLINE
INOUT
INPUT
INSENSITIVE
INSERT
INSTANCE
INSTANTIABLE
INSTEAD
INTEGRITY
INTERSECTION
INTERVAL
INTO
INVOKER
ISNULL
ISOLATION
JSON
JSON_ARRAY
JSON_ARRAYAGG
JSON_EXISTS
JSON_OBJECT
JSON_OBJECTAGG
JSON_QUERY
JSON_TABLE
JSON_TABLE_PRIMITIVE
JSON_VALUE
KEEP
KEY
KEYS
KEY_MEMBER
KEY_TYPE
LABEL
LAG
LANGUAGE
LARGE
LAST
LAST_VALUE
LATERAL
LEAD
LEADING
LEAKPROOF
LEAST
LEFT
LENGTH
LEVEL
LIBRARY
LIKE_REGEX
LIMIT
LINK
LISTAGG
LISTEN
LOAD
LOCAL
LOCALTIME
LOCALTIMESTAMP
LOCATION
LOCATOR
LOCK
LOCKED
LOG
LOG10
LOGGED
LOWER
MAP
MAPPING
MATCH
MATCHED
MATCHES
MATCH_NUMBER
MATCH_RECOGNIZE
MATERIALIZED
MAXVALUE
MEASURES
MEMBER
MERGE
MESSAGE_LENGTH
MESSAGE_OCTET_LENGTH
MESSAGE_TEXT
METHOD
MINUTE
MINVALUE
MODE
MODIFIES
MODULE
MONTH
MORE
MOVE
MULTISET
MUMPS
NAMESPACE
NATIONAL
NCHAR
NCLOB
NESTED
NESTING
NEW
NEXT
NFC
NFD
NFKC
NFKD
NIL
NO
NONE
NORMALIZE
NORMALIZED
NOTHING
NOTIFY
NOTNULL
NOWAIT
NTH_VALUE
NTILE
NULL
NULLABLE
NULLIF
NULLS
NUMBER
OBJECT
OCCURRENCES_REGEX
OCTETS
OCTET_LENGTH
OF
OFF
OFFSET
OIDS
OLD
OMIT
ONE
ONLY
OPEN
OPERATOR
OPTION
OPTIONS
ORDERING
ORDINALITY
OTHERS
OUT
OUTER
OUTPUT
OVER
OVERFLOW
OVERLAPS
OVERLAY
OVERRIDING
OWNED
OWNER
PAD
PARALLEL
PARAMETER
PARAMETER_MODE
PARAMETER_NAME
PARAMETER_ORDINAL_POSITION
PARAMETER_SPECIFIC_CATALOG
PARAMETER_SPECIFIC_NAME
PARAMETER_SPECIFIC_SCHEMA
PARSER
PARTIAL
PARTITION
PASCAL
PASS
PASSING
PASSTHROUGH
PASSWORD
PAST
PATH
PATTERN
PER
PERCENT
PERCENTILE_CONT
PERCENTILE_DISC
PERCENT_RANK
PERIOD
PERMISSION
PERMUTE
PLACING
PLAN
PLANS
PLI
POLICY
PORTION
POSITION
POSITION_REGEX
POWER
PRECEDES
PRECEDING
PRECISION
PREPARE
PREPARED
PRESERVE
PRIMARY
PRIOR
PRIVATE
PRIVILEGES
PROCEDURAL
PROCEDURE
PROCEDURES
PROGRAM
PRUNE
PTF
PUBLIC
PUBLICATION
QUOTE
QUOTES
RANGE
RANK
READ
READS
REASSIGN
RECHECK
RECOVERY
RECURSIVE
REF
REFERENCES
REFERENCING
REFRESH
REGR_AVGX
REGR_AVGY
REGR_COUNT
REGR_INTERCEPT
REGR_R2
REGR_SLOPE
REGR_SXX
REGR_SXY
REGR_SYY
REINDEX
RELATIVE
RELEASE
RENAME
REPEATABLE
REPLACE
REPLICA
REQUIRING
RESET
RESPECT
RESTART
RESTORE
RESTRICT
RESULT
RETURN
RETURNED_CARDINALITY
RETURNED_LENGTH
RETURNED_OCTET_LENGTH
RETURNED_SQLSTATE
RETURNING
RETURNS
REVOKE
RIGHT
ROLE
ROLLBACK
ROLLUP
ROUTINE
ROUTINES
ROUTINE_CATALOG
ROUTINE_NAME
ROUTINE_SCHEMA
ROW_COUNT
ROW_NUMBER
RULE
RUNNING
SAVEPOINT
SCALAR
SCALE
SCHEMA_NAME
SCOPE
SCOPE_CATALOG
SCOPE_NAME
SCOPE_SCHEMA
SCROLL
SEARCH
SECOND
SECTION
SECURITY
SEEK
SELECTIVE
SELF
SENSITIVE
SEQUENCE
SEQUENCES
SERIALIZABLE
SERVER
SERVER_NAME
SESSION
SESSION_USER
SET
SETOF
SETS
SHARE
SHOW
SIMILAR
SIMPLE
SIN
SINH
SIZE
SKIP
SNAPSHOT
SOME
SOURCE
SPACE
SPECIFIC
SPECIFICTYPE
SPECIFIC_NAME
SQL
SQLCODE
SQLERROR
SQLEXCEPTION
SQLSTATE
SQLWARNING
SQRT
STABLE
STANDALONE
START
STATE
STATEMENT
STATIC
STATISTICS
STDDEV_POP
STDDEV_SAMP
STDIN
STDOUT
STORAGE
STORED
STRICT
STRING
STRIP
STRUCTURE
STYLE
SUBCLASS_ORIGIN
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SUBSCRIPTION
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SUBSTRING
SUBSTRING_REGEX
SUCCEEDS
SUPPORT
SYMMETRIC
SYSID
SYSTEM
SYSTEM_TIME
SYSTEM_USER
TABLESAMPLE
TABLESPACE
TABLE_NAME
TAN
TANH
TEMP
TEMPLATE
TEMPORARY
TEXT
THROUGH
TIES
TIME
TIMESTAMP
TIMEZONE_HOUR
TIMEZONE_MINUTE
TO
TOKEN
TOP_LEVEL_COUNT
TRAILING
TRANSACTION
TRANSACTIONS_COMMITTED
TRANSACTIONS_ROLLED_BACK
TRANSACTION_ACTIVE
TRANSFORM
TRANSFORMS
TRANSLATE
TRANSLATE_REGEX
TRANSLATION
TREAT
TRIGGER
TRIGGER_CATALOG
TRIGGER_NAME
TRIGGER_SCHEMA
TRIM
TRIM_ARRAY
TRUNCATE
TRUSTED
UESCAPE
UNBOUNDED
UNCOMMITTED
UNCONDITIONAL
UNDER
UNENCRYPTED
UNIQUE
UNKNOWN
UNLINK
UNLISTEN
UNLOGGED
UNMATCHED
UNNAMED
UNNEST
UNTIL
UNTYPED
UPDATE
UPPER
URI
USAGE
USER
USER_DEFINED_TYPE_CATALOG
USER_DEFINED_TYPE_CODE
USER_DEFINED_TYPE_NAME
USER_DEFINED_TYPE_SCHEMA
USING
UTF16
UTF32
UTF8
VACUUM
VALID
VALIDATE
VALIDATOR
VALUE_OF
VARBINARY
VARIADIC
VAR_POP
VAR_SAMP
VERBOSE
VERSION
VERSIONING
VIEW
VIEWS
VOLATILE
WHENEVER
WHITESPACE
WIDTH_BUCKET
WINDOW
WITH
WITHIN
WITHOUT
WORK
WRAPPER
WRITE
ZONE

Answer 1

用游标计算啊。

USE [TEST]
GO

/****** Object:  Table [dbo].[TEST]    Script Date: 2021/11/12 10:52:39 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[TEST](
    [OrderID] [int] NULL,
    [OrderDate] [date] NULL,
    [CustomerID] [int] NULL
) ON [PRIMARY]

GO

declare @ID nvarchar(50)
declare @Date nvarchar(50)
begin 
 declare MyCursor cursor for         --定义游标cursor1
  Select customerID,orderDate From TEST Order By customerID,orderDate       --使用游标的对象(跟据需要填入select文)

            Open MyCursor
            -- 第一条
            Fetch next From MyCursor
            Into @ID,@Date
            -- 第二条
            While(@@Fetch_Status = 0)
                  Begin

                         Begin
                               Select @ID = Convert(Char(20),@ID)
                               Select @Date = Convert(Char(20),@Date)
                               PRINT @ID + ':' + @Date
                         End

                         Fetch next From MyCursor
                         Into @ID,@Date

                  End
            Close MyCursor
            Deallocate MyCursor
            end;

declare @ID nvarchar(50)
declare @Date nvarchar(50)
declare @PRE_ID nvarchar(50)
declare @NEXT_ID nvarchar(50)
declare @PRE_DATE nvarchar(50)
declare @NEXT_DATE nvarchar(50)
declare @DATEDIFF nvarchar(50)
begin 
 declare MyCursor cursor for         --定义游标cursor1
  Select customerID,orderDate From TEST Order By customerID,orderDate       --使用游标的对象(跟据需要填入select文)

            Open MyCursor
            -- 第一条
            Fetch next From MyCursor
            Into @ID,@Date
        
            While(@@Fetch_Status = 0)
                  Begin

                         Begin
                               --Select @ID = Convert(Char(20),@ID)
                               --Select @Date = Convert(Char(20),@Date)
                               PRINT @ID + ':' + @Date
                         End
                         Select @PRE_ID =@ID
                         Select @PRE_DATE =@Date
                         -- 第二条
                         Fetch next From MyCursor
                         Into @ID,@Date
                         Select @NEXT_ID =@ID
                         Select @NEXT_DATE =@Date
                         SELECT @DATEDIFF =  datediff( day, @PRE_DATE,@NEXT_DATE )
                         IF(@NEXT_ID = @PRE_ID)
                            PRINT @ID + ':' + @PRE_DATE+'-' + @NEXT_DATE+':'+@DATEDIFF
                  End
            Close MyCursor
            Deallocate MyCursor
            end;