I'm having an issue performing normal SELECT statements (that is, not the 'searches' they were designed to do- I'm not using MATCH). What I'm trying to do is query the table for all rows of an INTEGER column. However, the SELECT statement always returns no rows. I've inspected the database with an SQLite browser and the query should work. Here it is:
Here's the MAKE TABLE statement:
CREATE VIRTUAL TABLE FTS_journal USING fts3(journal_id INTEGER, journal_text_col TEXT)
And here's the SELECT:
SELECT journal_id FROM FTS_journal
Does it have something to do with my running a 'normal' query over a virtual table? I can't really think of any other reason
EDIT: I'm using Android's version of SQLite, meaning SQLite3. I know it supports FTS properly...
If any further information I can provide will help, please tell me and I will post it.
What you've written should work. Are you 100% positive you've actually inserted something into the table? Have you ran insert statements, and if so, are you sure they were successful?
I tested your statements, running the create statement, then the following statement:
insert into FTS_journal (journal_id, journal_text_col) values (1, 'test');
... then your select statement, and sqlite returned 1 row (journal_id, value 1) just as it should.
Related
Is there a way to access the SQLiteLog or at least pipe out errors to do with SQLite?
I would like to automatically send any errors, like the below, so I can optimise the database by adding in indexes, or making other changes as need be.
E/SQLiteLog: (284) automatic index on messages(chat_id)
It could well be that I'd only want to catch code 284, rather than getting everything. Is there a way of doing this when building the app, as would be useful to pass to crashlytics to help with development going forward
A potential alternative, would be to run the queries preceded with EXPLAIN QUERY PLAN, and to then check for AUTOMATIC COVERING INDEX in the results.
e.g.
DROP TABLE IF EXISTS table1;
DROP TABLE IF EXISTS table2;
CREATE TABLE IF NOT EXISTS table1 (column1 TEXT, column2 TEXT);
CREATE TABLE IF NOT EXISTS table2 (column3, column4);
EXPLAIN QUERY PLAN
SELECT * FROM table1, table2 WHERE column1=column3;
Results in :-
As you can see this is based upon a predication of the number of rows rather than the actual number of rows, so works if there is no data (as above), which could well be beneficial, from a development perspective, as opposed to trying to trap on a as happens basis.
I really have two questions:
1/ how to read/check sqlite db table offline?
2/ Why is a sqlite table column of boolean type set to NULL?
ad 1/ I have downloaded sqlite3.exe and when i use the cmd > .dump quotes_table i see all rows like
INSERT INTO quotes_table` VALUES................
INSERT INTO quotes_table` VALUES................
INSERT INTO quotes_table` VALUES................
INSERT INTO quotes_table` VALUES................
etc
Is this correct as i was expecting to see just the values and not the queries?
ad 2/ I alter+updated the quotes_table by
db.execSQL("ALTER TABLE quotes_table ADD COLUMN quoteUsed boolean");
db.execSQL("UPDATE 'quotes_table' SET quoteUsed = 0");
I read on http://www.sqlite.org/datatype3.html sqlite use 0 and 1 for boolean type so i thought putting quoteUsed = 0 should be OK, but the value reads NULL.
How can i fix this?
regards,
ps: FYI just installed SQLite manager addon for Firefox and it makes things easier
1/ how to read/check sqlite db table offline?
Normally, SQLite is used with local databases, so database exists or does not exists - "offline" doesn't apply.
2/ Why is a sqlite table column of boolean type set to NULL?
SQLite doesn't have a boolean data type. It's affinity is NUMERIC. Check Datatypes In SQLite Version 3
NULL values, as in other DBMS, means nothing assigned.
when i use the cmd > .dump quotes_table i see all rows like ...
DUMP is used to extract all data from database. Actually, it returns SQL statements you may use to rebuild a new database from scratch.
To get data only, use SQL queries (check SELECT statement).
when i use the cmd > .dump quotes_table i see all rows like
...
Is this correct as i was expecting to see just the values and not the queries?
Yes, .dump creates the SQL that would produce an identical database.
2/ I alter+updated the quotes_table by
...
I read on http://www.sqlite.org/datatype3.html sqlite use 0 and 1 for boolean type so i thought putting quoteUsed = 0 should be OK, but the value reads NULL. How can i fix this?
Nothing really wrong with the SQL. How are you reading the value?
I'm using a tutorial here to provide an AutoCompleteTextView with a SimpleCursorAdapter. It works perfectly as is, but I've changed the database to use fts3 because I've heard it's faster (hence, the name).
It seems something in the code is hard-wired to use the column _id because after changing to an fts3 table, I get this error:
01-28 21:31:53.018: E/AndroidRuntime(16284): java.lang.IllegalArgumentException: column '_id' does not exist
01-28 21:31:53.018: E/AndroidRuntime(16284): at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:314)
Even though I haven't declared the autoincrement key anywhere (as it's superceded by rowid in fts3). The error occurs in AbstractCursor, so there's not much I can do about it.
I'm thinking there might be a way to force the code to recognize rowid as _id by using SELECT rowid,* FROM mytable and then changing the column name somehow.. I'm pretty new to sql so any help is appreciated!
Renaming a column in SQLite can be done as described here. Note that it is highly advisable to do all these operations in transaction. One detail when you are doing this in Android - I don't know how you execute sql scripts in your solution, but keep in mind this if you use execSQL calls.
By the way if you prefer not to rename the column you can try the technique proposed here.
I created a table in the database that has the data like this:
Now i have written a query that updates the contact field by concatinating name and email fields:
UPDATE MyContacts SET contact=(SELECT name||'--'||email FROM MyContacts);
Here the problem is after executing the query the table is as below:
Why is it happening like this? In oracle i never faced this problem. Please help me. Thank you
Right now you're not specifying the correct row to retrieve the values from. Try something like this:
UPDATE MyContacts SET contact = name||'--'||email;
EDIT: Glad it worked. Your first issue was that your sub-select uses a SELECT statement with no WHERE clause (SELECT name||'--'||email FROM MyContacts will return 3 rows). One possible solution would be for SQLite to throw an error and say You've tried to set a column to the result of an expression that returns more than 1 row: I've seen this with MySQL and SQL Server. However, in this case SQLite appears to just use only the very first value returned. However, your second error then kicks in: since you don't narrow your UPDATE statement with a WHERE clause, it uses that first value returned to update EVERY single row, which is what you see.
Really all I want to do is say the query SELECT DISTINCT column FROM table but I can't figure out how to structure it in the enourmous query methods that are part of SQLiteDatabase
I'm just trying to get the names of all contacts in a table.
You seem to know the sql query you want to run. Have you tried using rawQuery()?
You will probably find this version of the SQLiteDatabase#query method most useful.