Doubt about Indexeddb

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I’m needing to do a many-to-many table on Indexeddb, where I have People Classes and People Classes, one can participate in several classes, and several classes can have several students, so I created this class table person, where I put people code, class code, a flag to identify who’s in that class. Follow the code of my table.

    var pessoa turma = db.createObjectStore("tbl_PESSOA_TURMA", {keyPath: "COD_IDENT_TURMA"});

pessoa_turma .createIndex("COD_IDENT_PESSO", "COD_IDENT_PESSO", {unique: false});
pessoa_turma .createIndex("COD_IDENT_CELUL", "COD_IDENT_TURMA", {unique: false});
pessoa_turma .createIndex("FLG_IDENT_PESSO", "FLG_IDENT_PESSO", {unique: false});
pessoa_turma .createIndex("COD_IDULT_ATUAL", "COD_IDULT_ATUAL", {unique: false});
pessoa_turma .createIndex("DAT_ULTIM_ATUAL", "DAT_ULTIM_ATUAL", {unique: false});

With this code I am only able to save some part of the class, because the class code is suffering a "group by", for example I have 16 people, and it appears only 3 classes, because these 16 people are in 3 different classes.

How do I accept the registration of more than one code ? I need the class code to look like a primary key, because in class research I need it to return to me all the codes of people who have class 'X code'.

database indexeddb

  • If this table is turma_pessoas, PK can’t just be the class code. You said yourself that this table is from an N-M relationship, that is, the PK should be COD_IDENT_TURMA and COD_IDENT_PESSO.

  • However Indexeddb does not allow this.

2 answers

2


In your case, the problem is that with PK is the COD_IDENT_TURMA field, it does not accept two records with the same key.

An alternative would be to make the table have the composite PK (COD_IDENT_TURMA and COD_IDENT_PESSO). But in his commenting you say that the IndexedDB can’t stand it.

So, a possible solution for you to store the information the way you want, is to create a new column (COD_PESSOA_TURMA) to be your PK.

|tbl_PESSOA_TURMA|
+----------------+
|COD_PESSOA_TURMA| (PK)
|COD_IDENT_TURMA |
|COD_IDENT_PESSOA|

This way, you will be able to enter records of multiple students from multiple classes without PK violation, since it will be a sequential ID.

Related question in the English OS

When the use of composite primary key is recommended?

  • I didn’t do it this way, and succeed. But this way will also work.

  • Then post the way you did. It may be that in the future it will help more people who come to have the same doubt.

1

The js stayed this way:

    bd =    db.transaction("tbl_PESSOA_CELULA").objectStore("tbl_PESSOA_CELULA"),
    singleKeyRange = IDBKeyRange.only(w_codigo_turma);

index = bd.index("COD_IDENT_TURMA");
index.openCursor(singleKeyRange).onsuccess = function(event) {
    var cursor = event.target.result;
    if (cursor) {           
       console.log(cursor.value.COD_IDENT_PESSO);
       cursor.continue();
    }

And the database I structured like this:

var pessoa_turma= db.createObjectStore("tbl_PESSOA_TURMA", { autoIncrement : true });

pessoa_turma.createIndex("COD_IDENT_PESSO", "COD_IDENT_PESSO", {unique: false});
pessoa_turma.createIndex("COD_IDENT_CELUL", "COD_IDENT_TURMA", {unique: false});
pessoa_turma.createIndex("FLG_IDENT_PESSO", "FLG_IDENT_PESSO", {unique: false});
pessoa_turma.createIndex("COD_IDULT_ATUAL", "COD_IDULT_ATUAL", {unique: false});
pessoa_turma.createIndex("DAT_ULTIM_ATUAL", "DAT_ULTIM_ATUAL", {unique: false});

In my database structured in order to create a key, autoincrement, this generates code in sequence for each record of the class person table, above to get the answer of the code of the students of a certain class, I created an index, to inform which field I want from the table, created an Idbkeyrange that allows me to create something to be compared, is the synonym of where in Mysql, and last I created a cursor, its function is to go through all the result obtained in the specified query.

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