Series Article Directory
[SQL development practical skills] series (1): those things that have to be said about SQL
[SQL development practical skills] series (2): simple single table query
[SQL development practical skills] series (3): those things about SQL sorting
[SQL Development Practical Skills] Series (4): Discuss the Precautions for Using UNION ALL and Empty String & UNION and OR from the Execution Plan
[SQL Development Practical Skills] Series (5): Look at the Efficiency of IN, EXISTS and INNER JOIN from the Execution Plan , we need to divide the scenarios and don’t memorize the online conclusion
[SQL Development Practical Skills] series (6): Look at the efficiency of NOT IN, NOT EXISTS and LEFT JOIN from the execution plan, and remember that internal and external association conditions should not be misplaced
[SQL Development Practical Skills] series ( Seven): Let’s talk about how to compare the difference data and the corresponding number of records in two tables under the premise of duplicate data
[SQL development practical skills] series (eight): talk about how to insert data, which is more flexible than constraints to restrict data insertion And how does an insert statement insert multiple tables at the same time
[SQL development practical skills] series (9): An update mistakenly updates other column data to be empty? Merge rewrite update! Give you five ways to delete duplicate data!
[SQL Development Practical Skills] Series (10): Starting from splitting strings, replacing strings, and counting the number of occurrences of strings
[SQL Development Practical Skills] Series (11): Take a few cases to talk about translate|regexp_replace| listagg|wmsys.wm_concat|substr|regexp_substr Commonly used functions
[SQL development practical skills] series (12): Three questions (how to sort the strings in alphabetical order after deduplicating the letters of the string? How to identify which strings contain numbers? How to convert delimited data into a multivalued IN list?)
[SQL Development Practical Skills] Series (13): Discuss common aggregate functions & see sum() over () through the execution plan to accumulate employee wages
[SQL Development Practical Skills] Series (14): Calculate the balance after consumption &Calculate the cumulative sum of bank turnover & calculate the top three employees in each department's salary
[SQL development practical skills] series (fifteen): Find the data information of the row where the most value is located and quickly calculate the sum of max/min() keep() over(), fisrt_value, last_value, ratio_to_report
[SQL development practical skills] series (16): time type operation in data warehouse (primary) day, month, year, hour, minute, second difference and time interval calculation [SQL
development Practical Skills] Series (Seventeen): Time type operations in data warehouses (primary) determine the number of working days between two dates, calculate the number of occurrences of each date in the week of the year, and determine the difference between the current record and the next record Number of days
[SQL development practical skills] series (18): time type operations in data warehouse (advanced) INTERVAL, EXTRACT and how to determine whether a year is a leap year and the calculation of the week [SQL development practical skills]
series (19): How to print the calendar of the current month or year with one SQL in the time type operation (advanced) in the data warehouse? How to determine the date of the first and last day of the week in a month?
[SQL Development Practical Skills] Series (20): Time Type Operations in Data Warehouse (Advanced) Obtain Quarter Start and End Time and How to Count Discontinuous Time Data
[SQL Development Practical Skills] Series (21): Data Time type operations in the warehouse (advanced) Identify overlapping date ranges, and summarize data at specified 10-minute intervals
[SQL development practical skills] series (22): Data warehouse report scenario ☞ Is the efficiency of the analysis function must be fast Chat 1 Talk about the implementation of result set paging and interlaced sampling
[SQL Development Practical Skills] Series (23): Data Warehouse Report Scenario ☞ How to de-duplicate data permutations and how to find the record containing the maximum and minimum values? Use the execution plan again to prove to you that the performance of the analysis function is not good. Must be high
[SQL development practical skills] series (24): data warehouse report scenario ☞ Detailed explanation of "row to column" and "column to row" through case execution plan [SQL development practical skills]
series (25 ): Data warehouse report scenario ☞ Duplicate data in the result set is only displayed once and the efficient way to write the salary difference of the calculation department and how to quickly group data
[SQL development practical skills] series (26): Data warehouse report scenario ☞ chat How ROLLUP and UNION ALL do group totals respectively and how to identify which rows are the result rows of the summary
Article Directory
foreword
The main content of this article is about the advanced operations of time type operations. These operations are also more difficult time operation cases in the data warehouse: how to print out the calendar of the current month or the calendar of the current year with one SQL ? ? ? How to count all the dates that belong to a certain day of the week in a year??? How to determine the first and last - the date of a certain day of the week in a certain month? ? ?
[SQL development practical skills] This series of bloggers writes as a review of old knowledge. After all, SQL development is very important and basic in data analysis scenarios. Interviews will often ask about SQL development and tuning experience. I believe that when I finish writing this A series of articles can also gain something, and you can also face SQL interviews with ease in the future~.
1. Determine all dates that belong to a certain day of the week within a year
This example requests to return all Fridays in the specified year, use the knowledge introduced earlier to enumerate the information of the whole year, and then filter it.
SQL> with t as
2 (select trunc(sysdate, 'y') + (level - 1) as dy
3 from dual
4 connect by level <=
5 (add_months(trunc(sysdate, 'y'), 12) - trunc(sysdate, 'y')))
6 select dy, to_char(dy, 'day') as 周五 from t where to_char(dy, 'd') = 6;
DY 周五
----------- ---------------------------------------------------------------------------
2023-1-6 星期五
2023-1-13 星期五
2023-1-20 星期五
2023-1-27 星期五
2023-2-3 星期五
2023-2-10 星期五
2023-2-17 星期五
2023-2-24 星期五
2023-3-3 星期五
2023-3-10 星期五
2023-3-17 星期五
2023-3-24 星期五
2023-3-31 星期五
2023-4-7 星期五
2023-4-14 星期五
2023-4-21 星期五
2023-4-28 星期五
2023-5-5 星期五
2023-5-12 星期五
2023-5-19 星期五
2023-5-26 星期五
2023-6-2 星期五
2023-6-9 星期五
2023-6-16 星期五
2023-6-23 星期五
2023-6-30 星期五
2023-7-7 星期五
2023-7-14 星期五
2023-7-21 星期五
2023-7-28 星期五
2023-8-4 星期五
2023-8-11 星期五
2023-8-18 星期五
2023-8-25 星期五
2023-9-1 星期五
2023-9-8 星期五
2023-9-15 星期五
2023-9-22 星期五
2023-9-29 星期五
2023-10-6 星期五
2023-10-13 星期五
2023-10-20 星期五
2023-10-27 星期五
2023-11-3 星期五
2023-11-10 星期五
2023-11-17 星期五
2023-11-24 星期五
2023-12-1 星期五
2023-12-8 星期五
2023-12-15 星期五
2023-12-22 星期五
2023-12-29 星期五
52 rows selected
The point of this example is to use to_char(dy, 'd')to judge, so as to avoid the influence of different client settings, such as:
SQL> select to_char(sysdate,'day')as day,to_char(sysdate,'d') as d from dual;
DAY D
--------------------------------------------------------------------------- ---------------------------------------------------------------------------
星期三 4
SQL> alter session set nls_language=american;
Session altered
SQL> select to_char(sysdate,'day')as day,to_char(sysdate,'d') as d from dual;
DAY D
--------------------------------------------------------------------------- ---------------------------------------------------------------------------
wednesday 4
SQL>
It can be seen that when the parameter "day" is used, the results returned by different character sets are different, but "d" is not affected.
2. Determine the date of the first and last day of the week in a month
In this example, it is required to return the first Monday and the last Monday of the current month. We can find the Monday of the next week that is seven days before the end of the previous month and the end of the current month respectively.
SQL> select next_day(trunc(sysdate,'mm')-1,2) as 第一周周一,
2 next_day(last_day(trunc(sysdate,'mm'))-7,2) as 最后一周的周一
3 from dual;
第一周周一 最后一周的周一
----------- -----------
2023-2-6 2023-2-27
3. Create a calendar for this month
Now there is a demand: you are required to write a sql to print out the calendar information of the current month.
Are you a little confused when you see this demand?
How to achieve it? ? ?
In fact, we can enumerate all the dates in the specified month and convert them to the corresponding week information, and then do a "row-column conversion" according to the week. I will show you a way to exchange rows and columns here, because it is not introduced pivot/unpivot, so just case whendo it.
SQL> with t as
2 (select trunc(sysdate, 'mm') + (level - 1) as dy
3 from dual
4 connect by level <=
5 (add_months(trunc(sysdate, 'mm'), 1) - trunc(sysdate, 'mm'))),
6 t1 as
7 (select to_char(dy, 'iw') as 所在周,
8 to_char(dy, 'dd') as 日期,
9 to_number(to_char(dy, 'd')) 周几
10 from t)
11 select max(case 周几
12 when 2 then
13 日期
14 end) 周一,
15 max(case 周几
16 when 3 then
17 日期
18 end) 周二,
19 max(case 周几
20 when 4 then
21 日期
22 end) 周三,
23 max(case 周几
24 when 5 then
25 日期
26 end) 周四,
27 max(case 周几
28 when 6 then
29 日期
30 end) 周五,
31 max(case 周几
32 when 7 then
33 日期
34 end) 周六,
35 max(case 周几
36 when 1 then
37 日期
38 end) 周天
39 from t1
40 group by 所在周
41 order by 所在周;
周一 周二 周三 周四 周五 周六 周天
--------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- ---------------------------------------------------------------------------
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28
SQL>
4. Annual Calendar
How to write a month's calendar was introduced earlier.
What if it is a year round? The way is very different! ! ! Just enumerate 365 days.
There is a small problem here, the data return value of the 53rd week to_char(日期,'iw')is wrong, and the first week is returned.
SQL> WITH x AS
2 (SELECT to_date('2013-12-27', 'yyyy-mm-dd') + (LEVEL - 1) AS d
3 FROM dual
4 CONNECT BY LEVEL <= 5)
5 SELECT d, to_char(d, 'day') AS DAY, to_char(d, 'iw') AS iw FROM x;
D DAY IW
----------- --------------------------------------------------------------------------- ---------------------------------------------------------------------------
2013-12-27 星期五 52
2013-12-28 星期六 52
2013-12-29 星期日 52
2013-12-30 星期一 01
2013-12-31 星期二 01
SQL>
This data needs case whento be processed.
SQL>
SQL> WITH x AS
2 (SELECT to_date('2013-12-27', 'yyyy-mm-dd') + (LEVEL - 1) AS d
3 FROM dual
4 CONNECT BY LEVEL <= 5),
5 x1 as
6 (SELECT d,
7 to_char(d, 'day') AS DAY,
8 to_char(d, 'mm') AS mm,
9 to_char(d, 'iw') AS iw
10 FROM x)
11 select d,
12 day,
13 mm,
14 iw,
15 case
16 when mm = 12 and iw = '01' then
17 '53'
18 else
19 iw
20 end as new_iw
21 from x1;
D DAY MM IW NEW_IW
----------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- ---------------------------------------------------------------------------
2013-12-27 星期五 12 52 52
2013-12-28 星期六 12 52 52
2013-12-29 星期日 12 52 52
2013-12-30 星期一 12 01 53
2013-12-31 星期二 12 01 53
SQL>
So the annual calendar can be queried as:
SQL> with t as
2 (select trunc(sysdate, 'y') as 本年年初,
3 add_months(trunc(sysdate, 'y'), 12) as 下年初
4 from dual),
5 t1 as
6 (select 本年年初 + (level - 1) as 日期
7 from t
8 connect by level <= 下年初 - 本年年初),
9 t2 as
10 (select 日期,
11 to_char(日期, 'mm') as 月份,
12 to_char(日期, 'iw') 所在周,
13 to_number(to_char(日期, 'd')) as 周几
14 from t1),
15 t3 as
16 (select 日期,
17 月份,
18 case
19 when 月份 = 12 and 所在周 = '01' then
20 '53'
21 else
22 所在周
23 end as 所在周,
24 周几
25 from t2)
26 select case
27 when lag(月份) over(order by 所在周) = 月份 then
28 null
29 else
30 月份
31 end as 月份,
32 所在周,
33 max(case 周几
34 when 2 then
35 日期
36 end) 周一,
37 max(case 周几
38 when 3 then
39 日期
40 end) 周二,
41 max(case 周几
42 when 4 then
43 日期
44 end) 周三,
45 max(case 周几
46 when 5 then
47 日期
48 end) 周四,
49 max(case 周几
50 when 6 then
51 日期
52 end) 周五,
53 max(case 周几
54 when 7 then
55 日期
56 end) 周六,
57 max(case 周几
58 when 1 then
59 日期
60 end) 周天
61 from t3
62 group by 月份, 所在周
63 order by 2;
月份 所在周 周一 周二 周三 周四 周五 周六 周天
--------------------------------------------------------------------------- --------------------------------------------------------------------------- ----------- ----------- ----------- ----------- ----------- ----------- -----------
01 01 2023-1-2 2023-1-3 2023-1-4 2023-1-5 2023-1-6 2023-1-7 2023-1-8
02 2023-1-9 2023-1-10 2023-1-11 2023-1-12 2023-1-13 2023-1-14 2023-1-15
03 2023-1-16 2023-1-17 2023-1-18 2023-1-19 2023-1-20 2023-1-21 2023-1-22
04 2023-1-23 2023-1-24 2023-1-25 2023-1-26 2023-1-27 2023-1-28 2023-1-29
05 2023-1-30 2023-1-31
02 05 2023-2-1 2023-2-2 2023-2-3 2023-2-4 2023-2-5
06 2023-2-6 2023-2-7 2023-2-8 2023-2-9 2023-2-10 2023-2-11 2023-2-12
07 2023-2-13 2023-2-14 2023-2-15 2023-2-16 2023-2-17 2023-2-18 2023-2-19
08 2023-2-20 2023-2-21 2023-2-22 2023-2-23 2023-2-24 2023-2-25 2023-2-26
09 2023-2-27 2023-2-28
03 09 2023-3-1 2023-3-2 2023-3-3 2023-3-4 2023-3-5
10 2023-3-6 2023-3-7 2023-3-8 2023-3-9 2023-3-10 2023-3-11 2023-3-12
11 2023-3-13 2023-3-14 2023-3-15 2023-3-16 2023-3-17 2023-3-18 2023-3-19
12 2023-3-20 2023-3-21 2023-3-22 2023-3-23 2023-3-24 2023-3-25 2023-3-26
13 2023-3-27 2023-3-28 2023-3-29 2023-3-30 2023-3-31
04 13 2023-4-1 2023-4-2
14 2023-4-3 2023-4-4 2023-4-5 2023-4-6 2023-4-7 2023-4-8 2023-4-9
15 2023-4-10 2023-4-11 2023-4-12 2023-4-13 2023-4-14 2023-4-15 2023-4-16
16 2023-4-17 2023-4-18 2023-4-19 2023-4-20 2023-4-21 2023-4-22 2023-4-23
17 2023-4-24 2023-4-25 2023-4-26 2023-4-27 2023-4-28 2023-4-29 2023-4-30
05 18 2023-5-1 2023-5-2 2023-5-3 2023-5-4 2023-5-5 2023-5-6 2023-5-7
19 2023-5-8 2023-5-9 2023-5-10 2023-5-11 2023-5-12 2023-5-13 2023-5-14
20 2023-5-15 2023-5-16 2023-5-17 2023-5-18 2023-5-19 2023-5-20 2023-5-21
21 2023-5-22 2023-5-23 2023-5-24 2023-5-25 2023-5-26 2023-5-27 2023-5-28
22 2023-5-29 2023-5-30 2023-5-31
06 22 2023-6-1 2023-6-2 2023-6-3 2023-6-4
23 2023-6-5 2023-6-6 2023-6-7 2023-6-8 2023-6-9 2023-6-10 2023-6-11
24 2023-6-12 2023-6-13 2023-6-14 2023-6-15 2023-6-16 2023-6-17 2023-6-18
25 2023-6-19 2023-6-20 2023-6-21 2023-6-22 2023-6-23 2023-6-24 2023-6-25
26 2023-6-26 2023-6-27 2023-6-28 2023-6-29 2023-6-30
07 26 2023-7-1 2023-7-2
27 2023-7-3 2023-7-4 2023-7-5 2023-7-6 2023-7-7 2023-7-8 2023-7-9
28 2023-7-10 2023-7-11 2023-7-12 2023-7-13 2023-7-14 2023-7-15 2023-7-16
29 2023-7-17 2023-7-18 2023-7-19 2023-7-20 2023-7-21 2023-7-22 2023-7-23
30 2023-7-24 2023-7-25 2023-7-26 2023-7-27 2023-7-28 2023-7-29 2023-7-30
31 2023-7-31
08 31 2023-8-1 2023-8-2 2023-8-3 2023-8-4 2023-8-5 2023-8-6
32 2023-8-7 2023-8-8 2023-8-9 2023-8-10 2023-8-11 2023-8-12 2023-8-13
33 2023-8-14 2023-8-15 2023-8-16 2023-8-17 2023-8-18 2023-8-19 2023-8-20
34 2023-8-21 2023-8-22 2023-8-23 2023-8-24 2023-8-25 2023-8-26 2023-8-27
35 2023-8-28 2023-8-29 2023-8-30 2023-8-31
09 35 2023-9-1 2023-9-2 2023-9-3
36 2023-9-4 2023-9-5 2023-9-6 2023-9-7 2023-9-8 2023-9-9 2023-9-10
37 2023-9-11 2023-9-12 2023-9-13 2023-9-14 2023-9-15 2023-9-16 2023-9-17
38 2023-9-18 2023-9-19 2023-9-20 2023-9-21 2023-9-22 2023-9-23 2023-9-24
39 2023-9-25 2023-9-26 2023-9-27 2023-9-28 2023-9-29 2023-9-30
10 39 2023-10-1
40 2023-10-2 2023-10-3 2023-10-4 2023-10-5 2023-10-6 2023-10-7 2023-10-8
41 2023-10-9 2023-10-10 2023-10-11 2023-10-12 2023-10-13 2023-10-14 2023-10-15
42 2023-10-16 2023-10-17 2023-10-18 2023-10-19 2023-10-20 2023-10-21 2023-10-22
43 2023-10-23 2023-10-24 2023-10-25 2023-10-26 2023-10-27 2023-10-28 2023-10-29
44 2023-10-30 2023-10-31
11 44 2023-11-1 2023-11-2 2023-11-3 2023-11-4 2023-11-5
45 2023-11-6 2023-11-7 2023-11-8 2023-11-9 2023-11-10 2023-11-11 2023-11-12
46 2023-11-13 2023-11-14 2023-11-15 2023-11-16 2023-11-17 2023-11-18 2023-11-19
47 2023-11-20 2023-11-21 2023-11-22 2023-11-23 2023-11-24 2023-11-25 2023-11-26
48 2023-11-27 2023-11-28 2023-11-29 2023-11-30
12 48 2023-12-1 2023-12-2 2023-12-3
49 2023-12-4 2023-12-5 2023-12-6 2023-12-7 2023-12-8 2023-12-9 2023-12-10
50 2023-12-11 2023-12-12 2023-12-13 2023-12-14 2023-12-15 2023-12-16 2023-12-17
51 2023-12-18 2023-12-19 2023-12-20 2023-12-21 2023-12-22 2023-12-23 2023-12-24
01 52 2023-1-1
12 52 2023-12-25 2023-12-26 2023-12-27 2023-12-28 2023-12-29 2023-12-30 2023-12-31
63 rows selected
SQL>
Through this example, we can see that using the with statement can make your thinking and code display very clear, and you can easily check whether the steps t, t1, t2, and t3 have achieved the expected purpose. This is one of the functions of the with statement one.
Summarize
The four time operation cases introduced in this chapter are still difficult. If you can reach this level, you can feel that the time type operations should be able to do a job with ease~