I am new to SQL. I want to check that a table exist in data base or not. If it does not exist than create it. Also I want to check that a record exist in table or not. If exists than update it with new data, If does not exist than insert a new record in table. Here is the code. I don't know how to check for a existing table,record.
import sqlite3 as lite
con = lite.connect('test.db')
cur = con.cursor()
con.execute('''CREATE TABLE EMPLOYEE
(ITEMA TEXT PRIMARY KEY NOT NULL,
ITEMB CHAR(50) NOT NULL,
ITEMC CHAR(50),
ITEM0 TEXT
ITEM1 TEXT
ITEM2 TEXT
ITEM3 TEXT
ITEM4 TEXT);''')
con.execute("INSERT INTO EMPLOYEE (ID,NAME,ADDRESS,MOBILE_NUMBER,TRANSPORT_FOR_LUNCH,ONLY_DROP,KIDS,ADULTS) \
VALUES (%s,%s',%s,%s,%s,%s,%s,%s)" %(ia,ib,ic,i0,i1,i2,i3,i4));
To test for table existence in sqlite, you can do something like:
cursor = con.cursor()
statement = "SELECT name FROM sqlite_master WHERE type='table';"
if (table_name,) in cursor.execute(statement).fetchall():
print "Table %s exists." % table_name
To update or create depending upon pre-existence of a record, sqlite allows the use of replace, which is an alias for insert or replace:
replace into table_name (columns) values (values)
CREATE TABLE EMPLOYEE IF NOT EXISTS ..
creates only if it does not exist
Related
I got lots of example to append/overwrite table in sql from AZ Databricks Notebook. But no single way to directly update, insert data using query or otherway.
ex. I want to update all row where (identity column)ID = 1143, so steps which I need to taken care are
val srMaster = "(SELECT ID, userid,statusid,bloburl,changedby FROM SRMaster WHERE ID = 1143) srMaster"
val srMasterTable = spark.read.jdbc(url=jdbcUrl, table=srMaster,
properties=connectionProperties)
srMasterTable.createOrReplaceTempView("srMasterTable")
val srMasterTableUpdated = spark.sql("SELECT userid,statusid,bloburl,140 AS changedby FROM srMasterTable")
import org.apache.spark.sql.SaveMode
srMasterTableUpdated.write.mode(SaveMode.Overwrite)
.jdbc(jdbcUrl, "[dbo].[SRMaster]", connectionProperties)
Is there any other sufficient way to achieve the same.
Note : Above code is also not working as SQLServerException: Could not drop object 'dbo.SRMaster' because it is referenced by a FOREIGN KEY constraint. , so it look like it drop table and recreate...not at all the solution.
You can use insert using a FROM statement.
Example: update values from another table in this table where a column matches.
INSERT INTO srMaster
FROM srMasterTable SELECT userid,statusid,bloburl,140 WHERE ID = 1143;
or
insert new values to rows where one of the existing column value matches
UPDATE srMaster SET userid = 1, statusid = 2, bloburl = 'https://url', changedby ='user' WHERE ID = '1143'
or just insert multiple values
INSERT INTO srMaster VALUES
(1, 10, 'https://url1','user1'),
(2, 11, 'https://url2','user2');
In SQL Server, you cannot drop a table if it is referenced by a FOREIGN KEY constraint. You have to either drop the child tables before removing the parent table, or remove foreign key constraints.
For a parent table, you can use the below query to get foreign key constraint names and the referencing table names:
SELECT name AS 'Foreign Key Constraint Name',
OBJECT_SCHEMA_NAME(parent_object_id) + '.' + OBJECT_NAME(parent_object_id) AS 'Child Table'
FROM sys.foreign_keys
WHERE OBJECT_SCHEMA_NAME(referenced_object_id) = 'dbo' AND
OBJECT_NAME(referenced_object_id) = 'PARENT_TABLE'
Then you can alter the child table and drop the constraint by its name using the below statement:
ALTER TABLE dbo.childtable DROP CONSTRAINT FK_NAME;
I created triggers after creating a database in oracle apex. When testing in SQL code everything was fine, they worked. In the application I have the Professors table and when I change the value of the column "name", in the Courses table the value of the column "professor_name" should change. However when I change the value of the column "name" in the Professors table it throws me the error.
Here is the trigger definition:
CREATE OR REPLACE TRIGGER profesori_upd
AFTER UPDATE OF ime on profesori
FOR EACH ROW
BEGIN
UPDATE kursevi set ime_profesora = :new.ime
where pr_jmbg= :new.jmbg_pr;
END;
Here is the table Proffesors:
CREATE TABLE PROFESORI( jmbg_pr VARCHAR2(13) PRIMARY KEY,
ime VARCHAR2(20) NOT NULL,
prezime VARCHAR2(20) NOT NULL,
id_spreme NUMBER(5) NOT NULL,
CONSTRAINT profesor_sprema_fk FOREIGN KEY (id_spreme) REFERENCES
STRUCNE_SPREME(id)
);
Here is the table Courses:
CREATE TABLE KURSEVI(
opis VARCHAR2(40),
id_jezik NUMBER(10) NOT NULL,
id_nivo NUMBER(10) NOT NULL,
pr_jmbg VARCHAR2(13) NOT NULL,
CONSTRAINT kurs_jezik_fk FOREIGN KEY (id_jezik) REFERENCES JEZICI(id_j),
CONSTRAINT kurs_nivo_fk FOREIGN KEY (id_nivo) REFERENCES NIVOI_KURSEVA(id_n),
CONSTRAINT kurs_profesor_fk FOREIGN KEY (pr_jmbg) REFERENCES PROFESORI(jmbg_pr),
CONSTRAINT kurs_pk PRIMARY KEY(id_jezik,id_nivo,pr_jmbg)
);
After denormalization I added columns ime_profesora and prezime_profesora to the table Courses:
ALTER TABLE KURSEVI
ADD ime_profesora VARCHAR2(20);
ALTER TABLE KURSEVI
ADD prezime_profesora VARCHAR2(20);
UPDATE KURSEVI SET ime_profesora=( SELECT ime FROM PROFESORI WHERE profesori.jmbg_pr=kursevi.pr_jmbg);
UPDATE KURSEVI SET prezime_profesora=( SELECT prezime FROM PROFESORI WHERE profesori.jmbg_pr=kursevi.pr_jmbg);
ALTER TABLE KURSEVI
MODIFY ime_profesora varchar2(20) not null;
ALTER TABLE KURSEVI
MODIFY prezime_profesora varchar2(20) not null;
Error occurs after I try to change the value of the column name in the application, it does not say what the error is.
I intend to create a table in sqlite3 with the column names in a list [item1,...]. I don't want to hard code the column names while creating the table because the number of columns and even names are dynamic. I want the correct syntax to get the column names directly from this list. Thank you. I'm using python.
You can do something like this:
import contextlib
import sqlite3
fields = ["field1", "field2", "field3"]
with contextlib.closing(sqlite3.connect(':memory:')) as conn:
cursor = conn.cursor()
columns = ", ".join("{field} TEXT".format(field=field) for field in fields)
cursor.execute("""
CREATE TABLE IF NOT EXISTS your_table(
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE,
{columns}
)
""".format(columns=columns))
conn.commit()
But, you should consider using an ORM, like SqlAlchemy. Here is a tutorial for that: https://www.pythoncentral.io/introductory-tutorial-python-sqlalchemy/
Edit
To go further, your insert statement could be built like this:
stmt = ("INSERT INTO mytable ({fields}) VALUES ({marks})"
.format(fields=", ".join(fields), marks=", ".join("?" * len(fields))))
For instance:
INSERT INTO mytable (field1, field2, field3) VALUES (?, ?, ?)
I have a table 'Person' with columns as 'Person_id as primary key','DOB' and 'place' as follows:
'Person'
Person_id |Name|DOB | place
Another table is "employee" where emp_id is primary key as follows:
'employee'
Person_id |emp_id|dateofjoin
And one more table "Details":
'Details'
emp_id|competency|rating
Now what i want is once i add the 'Person' table details the rest of the two tables as'employe' and 'Details' to get updated also with respect to the new Person added in the Person table. So, how can i have this using sql query? Also i want to clear that i am not very much familiar with database.
I think your after something like this ( for SQL Server ):
Create Procedure dbo.CreateMyEmployee ( #empName varchar(50),
#dob datetime,
#doj datetime,
#place as varchar(100),
#competency varchar(100),
#rating int)
As
Begin
Declare #empId int
Begin Transaction
Begin Try
Insert into Person (Name, DOB, Place)
Values ( #empName, #dob, #place)
Insert into employe (Name, dateofJoin) -- Assuming emp_id is identity columen
Values ( #empName, #doj)
Select #empId = SCOPE_IDENTITY()
Insert Into Details(emp_id, competency, rating)
Values (#empId, #competency, #rating)
Commit transaction
End Try
Begin Catch
Rollback Transaction
SELECT ERROR_NUMBER() AS ErrorNumber, ERROR_MESSAGE() AS ErrorMessage
End Catch
End
I am using this link.
I have connected my cpp file with Eclipse to my Database with 3 tables (two simple tables
Person and Item
and a third one PersonItem that connects them). In the third table I use one simple primary and then two foreign keys like that:
CREATE TABLE PersonsItems(PersonsItemsId int not null auto_increment primary key,
Person_Id int not null,
Item_id int not null,
constraint fk_Person_id foreign key (Person_Id) references Person(PersonId),
constraint fk_Item_id foreign key (Item_id) references Items(ItemId));
So, then with embedded sql in c I want a Person to have multiple items.
My code:
mysql_query(connection, \
"INSERT INTO PersonsItems(PersonsItemsId, Person_Id, Item_id) VALUES (1,1,5), (1,1,8);");
printf("%ld PersonsItems Row(s) Updated!\n", (long) mysql_affected_rows(connection));
//SELECT newly inserted record.
mysql_query(connection, \
"SELECT Order_id FROM PersonsItems");
//Resource struct with rows of returned data.
resource = mysql_use_result(connection);
// Fetch multiple results
while((result = mysql_fetch_row(resource))) {
printf("%s %s\n",result[0], result[1]);
}
My result is
-1 PersonsItems Row(s) Updated!
5
but with VALUES (1,1,5), (1,1,8);
I would like that to be
-1 PersonsItems Row(s) Updated!
5 8
Can somone tell me why is this not happening?
Kind regards.
I suspect this is because your first insert is failing with the following error:
Duplicate entry '1' for key 'PRIMARY'
Because you are trying to insert 1 twice into the PersonsItemsId which is the primary key so has to be unique (it is also auto_increment so there is no need to specify a value at all);
This is why rows affected is -1, and why in this line:
printf("%s %s\n",result[0], result[1]);
you are only seeing 5 because the first statement failed after the values (1,1,5) had already been inserted, so there is still one row of data in the table.
I think to get the behaviour you are expecting you need to use the ON DUPLICATE KEY UPDATE syntax:
INSERT INTO PersonsItems(PersonsItemsId, Person_Id, order_id)
VALUES (1,1,5), (1,1,8)
ON DUPLICATE KEY UPDATE Person_id = VALUES(person_Id), Order_ID = VALUES(Order_ID);
Example on SQL Fiddle
Or do not specify the value for personsItemsID and let auto_increment do its thing:
INSERT INTO PersonsItems( Person_Id, order_id)
VALUES (1,5), (1,8);
Example on SQL Fiddle
I think you have a typo or mistake in your two queries.
You are inserting "PersonsItemsId, Person_Id, Item_id"
INSERT INTO PersonsItems(PersonsItemsId, Person_Id, Item_id) VALUES (1,1,5), (1,1,8)
and then your select statement selects "Order_id".
SELECT Order_id FROM PersonsItems
In order to achieve 5, 8 as you request, your second query needs to be:
SELECT Item_id FROM PersonsItems
Edit to add:
Your primary key is autoincrement so you don't need to pass it to your insert statement (in fact it will error as you pass 1 twice).
You only need to insert your other columns:
INSERT INTO PersonsItems(Person_Id, Item_id) VALUES (1,5), (1,8)