sql
Question: Whenever we work with an ORM, it is common to fall into the problem of N+1 queries . It's something about performance, even called antipattern . But what is this problem really, why does it happen, what are its main causes and how, in theory, to solve them? I've …
Question: How to get the names of all database tables MySQL? How to get the attributes (name, type, etc…) of a certain table in MySQL database? Answer: To view the tables of a database: SHOW TABLES; To view the table structure with name, type, etc.: DESC nome_da_tabela;
Question: There is a request: declare @StartDate DateTime=’2016-01-01′, @EndDate DateTime=’2016-02-29′ BEGIN SET NOCOUNT ON; select id, ModifiedAt From Deals Where ModifiedAt between @StartDate and @EndDate END How to make the query run on 2016-01-01 to 2016-03-01 for date intervals '2016-01-01' to '2016-02-29' ? That is, you need to add the …
Question: If we re-access the table from the main query, we consider it "from scratch" or in a version truncated by the conditions from the main question. For instance: SELECT DISTINCT IDX1.<столбец_1> FROM <таблица_1> IDX1 INNER JOIN <таблица_2> IDX2 ON IDX1.<столбец_n> = IDX2.<столбец_m> AND IDX2.<столбец_1> IN (<список>) WHERE NOT EXISTS …
Question: I get an error when trying to get an array of values from an open cursor while updating data into a nested table with a custom data type. This is how I create a nested table with a custom type at the database level: CREATE OR REPLACE TYPE “FOO_STATUS” …
Question: I need to create a query that follows some rules and they are: gsm to repeat reason_delivery that is different status that has ANOMALY and appears as the 1st result (above the others) I'll give you an example of how the data appears, and what data I need to …
Get a result that appears in 1st position if it has a value specified in SQL Read More »
Question: using is not null for one field in the request everything works, I add 2 field and it gives an error. Tell me how can I check, for example, 30 fields in the database for emptiness? SELECT * FROM `datafrom` where `micur`, `mtimein` is not NULL OR myid='”.$umid.”‘” Answer: …
sql – How to check all fields of a table for emptyness using is not null? Read More »
Question: I have a table that records my records where one column writes the data_inicial and another column the data_final . I need to generate a report where the user searches all records that were between the period of for example 03/01/2017 to 03/31/2017. What I needed is to get …
Question: SELECT store.odyid ,g.FID ,sds.QUANTITY ,min(convert(date,doc1.DOC_DATE)) as min_date FROM [store.move] AS m INNER JOIN [STORE.DOC] AS doc1 ON m.id_doc = doc1.ID_DOC INNER JOIN [store.move.spec] AS sm ON m.id_doc = sm.id_doc INNER JOIN [STORE.DOC.SPEC] AS sds ON sm.id_doc_spec = sds.ID_DOC_SPEC INNER JOIN artikul_full ON sm.id_artikul_new = artikul_full.ID_artikul INNER JOIN STORE ON …
Question: In Firebird how to delete duplicate records, keeping only one of them? Someone could help me. I have this select, but it deletes all records, I use firebird 2.1 delete from vendaproduto where vendaproduto.pro_codigo in (select vendaproduto.pro_codigo from vendaproduto where VENDAPRODUTO.ven_codigo = 2432 having COUNT(*) != 1) Answer: There …
