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Copy tables between sqlite databases, qt, causes error


Copy tables between sqlite databases, qt, causes error

By : fernando zacarias
Date : November 19 2020, 03:59 PM
To fix the issue you can do I want to write the contents of my SQlite database on user click to another SQlite database. For this I am trying to make connections to two databases and do select query from one db and in transaction do insert query to another. But I gets error on connection creation itself. , We can read from the Qt documentation about QSqlDatabase :
code :
database = QSqlDatabase::addDatabase("QSQLITE", "database_Connection");
mHistoryDB = QSqlDatabase::addDatabase("QSQLITE", "mHistoryDB_Connection");


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Use of temp tables in SQLite databases

Use of temp tables in SQLite databases


By : rvmaretto
Date : March 29 2020, 07:55 AM
I wish this help you Temp tables make things easier for the programmer by letting the programmer break up a single complex query into multiple relatively simpler queries, and also by letting the programmer store results temporarily so they can be consulted multiple times for different purposes during the course of the program without having to be reinstantiated each time. The latter also makes things easier for the computer. The disk subsystem and CPU can take a little rest, so to speak.
An example of the former: let say you wanted to get all records where:
code :
                    the sale was in the eastern division
                    and involved one of the several new gizmos introduced last quarter
                    and occurred during the special 5-day bonanza sale

                    or

                    the sale was made by the boss's daughter
                    who floats from division to division
                    and the sale occurred at any time during the month of May
SQLite - How do you join tables from different databases?

SQLite - How do you join tables from different databases?


By : Muhammad Iqbal
Date : March 29 2020, 07:55 AM
will help you If ATTACH is activated in your build of Sqlite (it should be in most builds), you can attach another database file to the current connection using the ATTACH keyword. The limit on the number of db's that can be attached is a compile time setting(SQLITE_MAX_ATTACHED), currently defaults to 10, but this too may vary by the build you have. The global limit is 125.
code :
attach 'database1.db' as db1;
attach 'database2.db' as db2;
.databases
select
  *
from
  db1.SomeTable a
    inner join 
  db2.SomeTable b on b.SomeColumn = a.SomeColumn;
Merge all SQLite databases with different tables

Merge all SQLite databases with different tables


By : oZdevTH
Date : March 29 2020, 07:55 AM
will be helpful for those in need Is there a cheap/fast way to merge SQLite db files with different tables? , Just dump and restore:
code :
for db in a, b, c, d; { sqlite3 ${db}.db .dump | sqlite3 abcd.db }
$ ( echo '.mode insert destinationtablename'
    echo 'select * from sourcetablename;' 
  ) |  sqlite3 -batch -init - source.db \
    |  sqlite3 -batch destination.db
Mysql databases. Delete all tables with foreign keys. Copy all tables

Mysql databases. Delete all tables with foreign keys. Copy all tables


By : Dien Phuong Nam
Date : March 29 2020, 07:55 AM
I hope this helps . I have two databases. First database is used by site. Second is used for debuging by test site.
code :
#!/bin/bash
USERNAME=root
PASSWORD=xxx
DBFROM=xxx
DBTO=xxx
HOST=localhost

MYSQL_OPTS="-u $USERNAME -p$PASSWORD -h $HOST"

TABLES=$(mysql $MYSQL_OPTS -BNe "show tables" $DBTO | tr '\n' ',' | sed -e 's/,$//' | awk '{print "SET FOREIGN_KEY_CHECKS = 0;DROP TABLE IF EXISTS " $1 ";SET FOREIGN_KEY_CHECKS = 1;"}')
mysql $MYSQL_OPTS -BNe "$TABLES" $DBTO
mysqldump $MYSQL_OPTS $DBFROM | mysql $MYSQL_OPTS $DBTO
Merging two SQLite databases which both have junction tables

Merging two SQLite databases which both have junction tables


By : Adam Krasuski
Date : March 29 2020, 07:55 AM
around this issue If you don't care about duplicates, you could get the maximum ID from DB1, and add it to every ID in DB2. However, you said that name could be unique, so let's do this right.
I'm assuming that all id columns are INTEGER PRIMARY KEY, i.e., autoincrementing.
code :
ATTACH '...' AS db2;
INSERT INTO Fruit(name)
SELECT name
FROM db2.Fruit
WHERE name NOT IN (SELECT name
                   FROM Fruit);
INSERT INTO Juice(name)
SELECT name
FROM db2.Juice
WHERE name NOT IN (SELECT name
                   FROM Juice);
INSERT INTO Recipe(juice_id, fruit_id)
SELECT (SELECT id
        FROM Juice
        WHERE name = (SELECT name
                      FROM db2.Juice
                      WHERE id = Recipe2.juice_id)),
       (SELECT id
        FROM Fruit
        WHERE name = (SELECT name
                      FROM db2.Fruit
                      WHERE id = Recipe2.fruit_id))
FROM db2.Recipe AS Recipe2;
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