rdbms

问题 Please help me understand further the many to many relationship. Suppose I have Teacher and Students Table and in my understanding it is one-to- many . Teacher TeacherId Primary Key TeacherName Student StudentId Primary Key TeacherId Foreign Key StudentName TeacherId can appear several times in the Student Table. I'm confused because Student can have many teacher. When can I say something is one-to-many and when is it many to many ? I can say One Student can have many teacher. On the other

问题 Comparing two comma separated values in sql, we can get done by using Split kind of functions.(Three columns also we can do !) But, without using the functions is that possible? Let me give an example. The query should check the following conditions (1) Select the tasks from Table- 1 That is Planned. But Not in done or declined columns. (2) Return only the mandatory tasks Using Split functionality(UD Functions) or Cursor is making query more complex and it swallows the time as well. Is there

问题 I have a table named Groups with primary key = Pkey . In Group there is a recursive association Parent_group references Pkey . I defined a Parent_Group as foreign key in relation Groups . I am using MYSQL. Table bame: Groups +------+-----------+------------+----------+---------------+ | PKey | GroupName | Region | Role | Parent_Group | +------+-----------+------------+----------+---------------+ | k1 | RootGroup | Jaipur | Admin | NULL | +------+-----------+------------+----------+-----------

问题 I'm writing some JDBC code which calls a Oracle 11g PL/SQL procdedure which has a Custom Object return type. I can get the code to call the procedure, but how do I access the returned Custom Object to obtain it's contained values?. An example of my code calling the procedure is below: PLSQL Code: Procedure GetDataSummary (p_my_key IN KEYS.MY_KEY%TYPE, p_recordset OUT data_summary_tab, p_status OUT VARCHAR2); Java Code: String query = "begin manageroleviewdata.getdatasummary(?, ?, ?); end;");

问题 Are there any PHP ORM projects which supports MySQL and NoSQL databases such as MongoDB? I am currently using RedBean to do MySQL ORM, however I woud like to introduce MongoDB to the applicatoin and perhaps even replace some of the MySQL with MongoDB in the future. An ORM that can allow me to easily transition between both would be nice. However, I tend to not like ORM that requires too much configuration (i.e. YAML, XML etc). RedBean is very nice in that it allows one to easily get things

问题 Happy new year everyone. I will ask my last question for this evening. I was wondering if it's possible in MS Access to make a column positive only. Since my approach of getting the exact number will only work if the column is >0. So when a number is <0 I want it to be 0 or 'notthing' This is the whole code (((([Factuur]![EindKMStand]-[Factuur]![BeginKMStand])-([Factuur]![Dagen]*125))*[Prijzen]![ExtraKM])+([Prijzen]![dag125KM]*[Factuur]![Dagen])) AS TotaalPrijs This part have to be 0> or =0 (

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 4 years ago . I am not so into database and I have to implement an insert this insert query on an Oracle db: insert into CODA_RX (PK_CODA, FK_TIPO_DOC, FK_PIVA_DESTINATARIO, DATA_IN, FK_STATO, DATA_OUT, CANALE, SIZE_XML, FK_PIVA_MITTENTE) values(70030, 5, 06655971007, '06-MAG-15', 2, '06-MAG-15', 'WEB', 553,

问题 From https://stackoverflow.com/a/51087864/3284469 primary keys can be primary indices. Must the search key of a primary index be or related to a primary key ? Will the answer be different in PostgreSQL and other DBMS? Thanks. 回答1: Postgres doesn't have "primary index", all indexes are implemented the same way, and point directly to the data rows. Must the search key of a primary index be or related to a primary key It must be a search on the expression used to form the primary index. if the

问题 I have a table "theaters". In which (theater_name,area_name,station) are composite key.And in the table "cubelists" I have columns (thtr_name,area,stn) which are to be referred to (theater_name,area_name,station) of table "theaters". The problem here is the combination of the columns - (theater_name,area_name,station) in table "theaters" is unique as it is a composite key. But each column separately is not unique. Then how can I refer these columns from table "cubelists"? Schema::create(

问题 I have strange (?) problem with ordering in Postgres by foreign key. It's second table & query that takes much longer with order by than without. EXPLAIN ANALYZE SELECT "spoleczniak_zdjecia"."id", "spoleczniak_zdjecia"."postac_id", "spoleczniak_zdjecia"."zdjecie", "spoleczniak_zdjecia"."opis", "spoleczniak_zdjecia"."data", "spoleczniak_zdjecia"."avatar", "spoleczniak_zdjecia"."tagi", "postac_postacie"."id", "postac_postacie"."user_id", "postac_postacie"."avatar", "postac_postacie"."ikonka",