I have created a backup of a given table using the following raw queries:
DB::statement("DROP TABLE IF EXISTS answers_bup");
DB::statement("CREATE TABLE answers_bup AS TABLE answers");
The answers table has the following schema:
CREATE TABLE answers
(
id uuid NOT NULL,
user_id uuid NOT NULL,
survey_id uuid NOT NULL,
question_id uuid NOT NULL,
answer character varying(255) NOT NULL,
created_at timestamp(0) without time zone NOT NULL,
updated_at timestamp(0) without time zone NOT NULL,
}
Now, in order to restore a single row, from the answers_bup table to the answers table. I wrote the following DB::insert:
$void = DB::insert("INSERT INTO answers
SELECT
'?'::uuid AS id,
'?'::uuid AS user_id,
'?'::uuid AS survey_id,
'?'::uuid AS question_id,
answer,
created_at,
updated_at
FROM
answers_bup
WHERE
id='?'::uuid", [
$newId,
$user_id,
$survey_id,
$question_id,
$answer->id
]);
Basically, I only need to copy over three fields from the answers_bup table - answer, created_at and updated_at. The others, have to be assigned new values, hence the above statement.
When I run this code fragment, I get no errors. Yet, the insert does not happen. The answers table remains empty.
Could anyone help me understand what might be wrong here?
Try DB::statement(), or DB::table('answers')->insert('...')
Related
I'm creating a project with laravel 6. One of my table column type is json.
The data format in the table column is like this:{age:30, gender:male, nation:china,...}. I am wondering if there is a way for me to set index for this column with laravel migration. my database version is mysql 8.0.21.
thank you!
I found this article very helpful for figuring this out. So for your example structure above, you might have a migration that looks like the following:
public function up(){
Schema::create('my_table', function(Blueprint $table){
$table->bigIncrements('id');
$table->json('my_json_col')->nullable();
$table->timestamps();
// add stored columns with an index
// index in this is optional, but recommended if you will be filtering/sorting on these columns
$table->unsignedInteger('age')->storedAs('JSON_UNQUOTE(my_json_col->>"$.age")')->index();
$table->string('gender')->storedAs('JSON_UNQUOTE(my_json_col->>"$.gender")')->index();
$table->string('nation')->storedAs('JSON_UNQUOTE(my_json_col->>"$.nation")')->index();
});
}
And this is equivalent to the following mysql statement:
create table my_table
(
id bigint unsigned auto_increment primary key,
my_json_col json null,
created_at timestamp null,
updated_at timestamp null,
age int unsigned as (json_unquote(json_unquote(json_extract(`my_json_col`, _utf8mb4'$.age')))) stored,
gender varchar(255) as (json_unquote(json_unquote(json_extract(`my_json_col`, _utf8mb4'$.gender')))) stored,
nation varchar(255) as (json_unquote(json_unquote(json_extract(`my_json_col`, _utf8mb4'$.nation')))) stored
)
collate = utf8mb4_unicode_ci;
create index my_table_age_index
on my_table (age);
create index my_table_gender_index
on my_table (gender);
create index my_table_nation_index
on my_table (nation);
And a simple view of the table after creation:
This example created actual stored columns, which for this scenario i think is what you would want. But you can also make virtual columns, which are created at query time instead of persistent columns, and you would just use the virtualAs function instead of the storedAs function in the migration.
These functions are documented in the Column Modifiers section of the Laravel migration docs, but it doesn't go into detail on JSON columns, this requires a bit more mysql knowledge.
I also found this article helpful for the mysql side of things for the JSON columns (SemiSQL).
I have a table:
create table employee (
employee_id NUMBER NOT NULL,
name VARCHAR2(255) NOT NULL,
notes VARCHAR2(4000),
created_by varchar2(255) not null,
created_at date default sysdate not null,
updated_by varchar2(255) not null,
updated_at date default sysdate not null,
PRIMARY KEY(vendor_id)
);
so when I insert from SQL developer:
insert into employee(employee_id, name,notes) values(1,'xyz','test');
it auto populates create_by, created_at, updated_at and updated_by.
row gets inserted successfully.
Whereas if I try to insert using cx_Oracle module in python,
cursor.execute("INSERT INTO employee VALUES (:employee_id,:name,:notes)",
{
'employee_id' : max_value,
'name' : each_vendor,
'notes' : 'test'
}
)
it throws error saying not enough values.
Why do I get this error? How can I solve it?
The answer is very simple, and has nothing to do with python. Your 2 insert statements are very different.
In the 1st, you explicitly name the columns you intend to provide values for: (employee_id, name,notes). However, in the insert statement used from Python, you don't specify the 3 columns by name. As a result, your insert statement expects you to provide the values for all columns in the table.
The fix: explicitly name the 3 columns:
cursor.execute("INSERT INTO employee (employee_id, name, notes) VALUES (:employee_id,:name,:notes)",
{
'employee_id' : max_value,
'name' : each_vendor,
'notes' : 'test'
}
)
Hey I have two columns in my HIVE table :
For example :-
c1 : name
c2 : age
Now while creating a table I want to declare two more columns which automatically give me the current date and time when the row is loaded.
eg: John 24 26/08/2015 11:15
How can this be done?
Hive currently does not support the feature to add a default value to any column definition while creating a table. Please refer to the link for complete hive create table syntax:
Hive Create Table specification
Alternative work around for this issue would be to temporarily load data into temporary table and use the insert overwrite table statement to add the current date and time into the main table.
Below example may help:
1. Create a temporary table
create table EmpInfoTmp(name string, age int);
2. Insert data using a file or existing table into the EmpInfoTmp table:
name|age Alan|28 Sue|32 Martha|26
3. Create a table which will contain your final data:
create table EmpInfo(name string, age tinyint, createDate string, createTime string);
4. Insert data from the temporary table and with that also add the columns with default value as current date and time:
insert overwrite table empinfo select name, age, FROM_UNIXTIME( UNIX_TIMESTAMP(), 'dd/MM/YYYY' ), FROM_UNIXTIME( UNIX_TIMESTAMP(), 'HH:mm' ) from empinfofromfile;
5. End result would be like this:
name|age|createdate|createtime Alan|28|26/08/2015|03:56 Martha|26|26/08/2015|03:56 Sue|32|26/08/2015|03:56
Please note that the creation date and time values will be entered accurately by adding the data to your final table as and when it comes into the temp table.
Note: You can't set more then 1 column as CURRENT_TIMESTAMP.
Here this way, You cant set CURRENT_TIMESTAMP in one column
SQL:
CREATE TABLE IF NOT EXISTS `hive` (
`id` int(11) NOT NULL,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`age` int(11) DEFAULT '0',
`datecreated` timestamp NULL DEFAULT CURRENT_TIMESTAMP
);
Hey i found a way to do it using shell script.
Heres how :
echo "$(date +"%Y-%m-%d-%T") $(wc -l /home/hive/landing/$line ) $dir " >> /home/hive/recon/fileinfo.txt
Here i get the date without spaces. In the end I upload the textfile to my hive table.
I'm wondering is it possible to use a constraint to set the value of one column to be sum of two others. For example given the following tables:
CREATE TABLE Room (
Room_Num NUMBER(3),
Room_Band_ID NUMBER(2),
Room_Type_ID NUMBER(2),
Room_Price NUMBER(4),
PRIMARY KEY (Room_Num),
FOREIGN KEY(Room_Band_ID)
REFERENCES Room_Band(Room_Band_ID),
FOREIGN KEY(Room_Type_ID)
REFERENCES Room_Type(Room_Type_ID)
);
CREATE TABLE Booking (
Booking_ID NUMBER(10) NOT NULL,
GuestID NUMBER(4) NOT NULL,
StaffID NUMBER(2) NOT NULL,
Payment_ID NUMBER(4) NOT NULL,
Room_Num NUMBER(3) NOT NULL,
CheckInDate DATE NOT NULL,
CheckOutDate DATE NOT NULL,
Booking NUMBER(2) NOT NULL,
Price NUMBER(4),
PRIMARY KEY (Booking_ID),
FOREIGN KEY(GuestID)
REFERENCES Guest(GuestID),
FOREIGN KEY(StaffID)
REFERENCES Staff(StaffID),
FOREIGN KEY(Payment_ID)
REFERENCES Payment(Payment_ID),
FOREIGN KEY(Room_Num)
REFERENCES Room(Room_Num)
);
I know it is possible to do something like:
Constraint PriceIs CHECK (Booking.Price=(Room.Room_Price*
(Booking.CheckOutDate - Booking.CheckInDate)));
Is it also possible to set up a constraint that doesn't just ensure that the price is correct, but to calculate the price automatically into the price field for the relevant tuple?
Update,
So I've tried to set up a trigger as follows:
CREATE OR REPLACE trigger PriceCompute
AFTER INSERT ON Booking
FOR each row
BEGIN
UPDATE Booking
SET
SELECT (Room.Room_Price*(Booking.CheckOutDate - Booking.CheckInDate))
INTO
Booking.Price
FROM Booking
JOIN ROOM ON Booking.Room_Num = Room.Room_Num
END;
/
But I'm getting the following errors back:
Can anyone see where I'm going astray here, as its beyond me.
Yes, you can. Here are your options. Listed in order of my personal preference:
You can have a table without this column. And create a view that will be calculating this column on a fly.
You may use oracle virtual columns
create table Room (
...
price NUMBER GENERATED ALWAYS AS (room_price*(checkOut-checkIn)) VIRTUAL,
...)
You may use actual column (same as 2, per Dave Costa):
create table Room (
...
price AS (room_price*(checkOut-checkIn)),
...)
You can write trigger to populate it (like Mat M suggested)
You can write stored procedure, but it will be an overkill in this situation
I think you would have to put a trigger on both tables for whenever the price value of the room is changed or the checkout/in dates are changed, it will update the PriceIs field from your calculation.
If you don't need the calculated portion stored in an actual field, you can always create a view that calculates it whenever you look at the view.
I think the better solution is to use a view that calculates the value on the fly. But regarding your attempt to create a trigger, you should use :new.<column_name> to refer to the values being inserted into the Booking table. You don't need to perform updates and queries on that table to get or modify the values in the row that is being inserted*. You just refer to them as variables. So you would want to do something like:
SELECT (Room.Room_Price*(:new.CheckOutDate - :new.CheckInDate))
INTO
:new.Price
FROM ROOM WHERE :new.Room_Num = Room.Room_Num
*In fact, you can't perform queries or updates on the table whose modification invoked the trigger in the first place. You would get the infamous "mutating table" error if your trigger actually compiled and ran.
I am trying to use the "Create Table As Select" feature from Oracle to do a fast update. The problem I am seeing is that the "Null" field is not being preserved.
I defined the following table:
create table mytable(
accountname varchar2(40) not null,
username varchar2(40)
);
When I do a raw CTAS, the NOT NULL on account is preserved:
create table ctamytable as select * from mytable;
describe ctamytable;
Name Null Type
----------- -------- ------------
ACCOUNTNAME NOT NULL VARCHAR2(40)
USERNAME VARCHAR2(40)
However, when I do a replace on accountname, the NOT NULL is not preserved.
create table ctamytable as
select replace(accountname, 'foo', 'foo2') accountname,
username
from mytable;
describe ctamytable;
Name Null Type
----------- ---- -------------
ACCOUNTNAME VARCHAR2(160)
USERNAME VARCHAR2(40)
Notice that the accountname field no longer has a null, and the varchar2 field went from 40 to 160 characters. Has anyone seen this before?
This is because you are no longer selecting ACCOUNTNAME, which has a column definition and meta-data. Rather you are selecting a STRING, the result of the replace function, which doesn't have any meta-data. This is a different data type entirely.
A (potentially) better way that might work is to create the table using a query with the original columns, but with a WHERE clause that guarantees 0 rows.
Then you can insert in to the table normally with your actual SELECT.
By having query of 0 rows, you'll still get the column meta-data, so the table should be created, but no rows will be inserted. Make sure you make your WHERE clause something fast, like WHERE primary_key = -999999, some number you know would never exist.
Another option here is to define the columns when you call the CREATE TABLE AS SELECT. It is possible to list the column names and include constraints while excluding the data types.
An example is shown below:
create table ctamytable (
accountname not null,
username
)
as
select
replace(accountname, 'foo', 'foo2') accountname,
username
from mytable;
Be aware that although this syntax is valid, you cannot include the data type. Also, explicitly declaring all the columns somewhat defeats the purpose of using CREATE TABLE AS SELECT.