如何从 postgresql 中的以下数据中为相应的 itemname 获取最新的可用库存值？

Question

Refer to the following sample data.

|availablestock  |  itemname  |  tdate            |
|----------------|------------|-------------------|
|86              |ABC         |2020-01-29 19:44:43|
|90              |ABC         |2020-01-27 19:32:59|
|88              |ABC         |2020-01-29 19:46:35|
|100             |Soap        |2020-01-26 19:46:35|
|98              |Soap        |2020-02-29 19:46:35|

The following result needed-

|availablestock  |  itemname  |  tdate            |
|----------------|------------|-------------------|
|88              |ABC         |2020-01-29 19:46:35|
|98              |Soap        |2020-02-29 19:46:35|

Answer 1

Do you need below -

SELECT max(availablestock)
FROM YOUR_TABLE
WHERE tdate BETWEEN '2020-01-20' AND '2020-01-29'

Answer 2

I think you are looking for order by and limit

SELECT availablestock FROM TABLE 
WHERE TDATE BETWEEN '2020-01-20' AND '2020-01-29' 
ORDER BY TDATE DESC LIMIT 1

CHECK DEMO HERE

Answer 3

Test Script

DROP TABLE IF EXISTS "Items";
CREATE TABLE IF NOT EXISTS "Items"
(
    "Id" SERIAL NOT NULL PRIMARY KEY,
    "Name" VARCHAR(64) NOT NULL,
    "Stock" INT NOT NULL,
    "TDate" TIMESTAMP NOT NULL
);

INSERT INTO "Items"("Name", "Stock", "TDate") VALUES ('ABC', 86, '2020-01-29 19:44:43');
INSERT INTO "Items"("Name", "Stock", "TDate") VALUES ('ABC', 90, '2020-01-27 19:32:59');
INSERT INTO "Items"("Name", "Stock", "TDate") VALUES ('ABC', 88, '2020-01-29 19:46:35');


SELECT * FROM "Items"
WHERE "TDate" <@ tsrange('[2020-01-20 00:00:00 , 2020-01-30)') 
--//Included lowerbound and excluded upper bound -- Valid values 2020-01-20 00:00:00 to 2020-01-29 23:59:59
ORDER BY "TDate" DESC
LIMIT 1

In the text form of a range, an inclusive lower bound is represented by "[" while an exclusive lower bound is represented by "(". Likewise, an inclusive upper bound is represented by "]", while an exclusive upper bound is represented by ")"

---

The result in PgAdmin4 connected to a PostgreSQL 10 instance

---

References:

• Range Functions and Operators
• Range Types