hi please how do i give sql column maximum input example if i want max_num column to take only three(3) result sets or inputs
It's mostly the same in other rdbms. You need to specify right after the column type
MYSQL
CREATE TABLE TestTable(
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
three_char_demo VARCHAR(3) NOT NULL,
)
PostgreSQL
CREATE TABLE TestTable(
ID INT PRIMARY KEY NOT NULL,
three_char_demo CHAR(3) NOT NULL,
);
Related
CREATE TABLE identity (
empid VARCHAR(255) PRIMARY KEY,
entry VARCHAR(255)
);
-- Table: vectors
CREATE TABLE vectors (
f_id INTEGER PRIMARY KEY IDENTITY(1,1),
label STRING NOT NULL,
empid STRING REFERENCES identity (empid)
NOT NULL,
vector BLOB NOT NULL
);
I tried to run the above query but it gives me error
Incorrect syntax near expected '.', ID or QUOTED_ID.
I don't understand why it is giving me this error, is it because IDENTITY is a keyword in SQL Server. Kindly help!
Try this:
CREATE TABLE [identity] (
empid VARCHAR(255) PRIMARY KEY,
entry VARCHAR(255)
);
-- Table: vectors
CREATE TABLE vectors (
f_id INTEGER PRIMARY KEY IDENTITY(1,1),
label VARCHAR(255) NOT NULL,
empid VARCHAR(255) REFERENCES [identity] (empid)
NOT NULL,
vector VARCHAR(255) NOT NULL
);
Also, if you are working with SQL Server Management Studio, you can see that some words are colored in blue. It will be better to avoid them using in your code as names of tables, variables and other objects. For example, identity is such word.
I need to use indexing to query a varchar virtual generated column from a JSON column, but I'm not sure why the index is not being used. Is it because of the varchar type?
Table DDL
create table dp_order
(
id bigint unsigned auto_increment primary key,
detail longtext collate utf8mb4_bin default '{}' not null,
phone_number varchar(20) as (json_value(`detail`, '$.phone_number')),
constraint detail check (json_valid(`detail`))
)
create index dp_order_phone_number
on dp_order (phone_number);
Query
EXPLAIN
(SELECT *
FROM dp_order
WHERE phone_number = '081234567890');
Result
id,select_type,table,type,possible_keys,key,key_len,ref,rows,Extra
1,SIMPLE,dp_order,ALL,dp_order_phone_number,,,,34,Using where
MariaDB version 10.5.12-MariaDB-1:10.5.12+maria~focal
Let's say I have a table tree and a table special_tree
CREATE TABLE tree VALUES (name VARCHAR(32) UNIQUE NOT NULL PRIMARY KEY,
type VARCHAR(32) NOT NULL);
CREATE TABLE special_tree VALUES (name NOT NULL REFERENCES tree(name),
treat_date DATE,
id INT NOT NULL PRIMARY KEY);
So I have a table containing a list of trees with unique names BUT I want to say that a tree can have multiple 'treat_date' (for various reasons).
Since tree(name) is unique I can't add 2 same name in special_tree.
Is the only solution is to remove unique from tree and then add everywhere i handle the tree table an IF statement to check if name isn't already there? (IF EXISTS (SELECT name FROM tree where tree.name = ...))
If you consider the column name of the table tree it doesn't mean that all referenced columns also should have unique values. Take a look at this example
the best solution for this is (for MySQL):
CREATE TABLE tree VALUES (
id_t int(11) NOT NULL auto_increment,
name VARCHAR(32) NOT NULL,
type VARCHAR(32) NOT NULL,
CONSTRAINT tree_pk PRIMARY KEY (id_t));
CREATE TABLE special_tree VALUES (
id_st int(11) NOT NULL auto_increment,
id_t NOT NULL REFERENCES tree(id_t),
treat_date DATE,
CONSTRAINT special_tree_pk PRIMARY KEY (id_st));
for PostgreSQL:
CREATE TABLE tree VALUES (
id_t serial primary key,
name VARCHAR(32) NOT NULL,
type VARCHAR(32) NOT NULL);
CREATE TABLE special_tree VALUES (
id_st serial primary key,
id_t NOT NULL REFERENCES tree(id_t),
treat_date DATE);
CREATE TABLE employees (
id INT NOT NULL auto_increment PRIMARY KEY (ID),
first_name VARCHAR(20) DEFAULT NULL,
last_name VARCHAR(20) DEFAULT NULL,
salary INT DEFAULT NULL);
I think this is correct query to create table in Oracle database.. but it gives the following error:
ORA-00907: missing right parenthesis
How to correct the statement?
You can validate your SQL using formatting tools such as http://www.dpriver.com/pp/sqlformat.htm
auto_increment seems like a proprietary MySQL extension, so it's not valid for Oracle.
also, "id int not null auto_increment primary key (id)" does not need the last "(id)"
Using Oracle, you shoud try something like this
CREATE SEQUENCE seq;
CREATE TABLE employees
(
id INTEGER NOT NULL PRIMARY KEY,
first_name VARCHAR2(20) DEFAULT NULL,
last_name VARCHAR2(20) DEFAULT NULL,
salary INTEGER DEFAULT NULL
);
INSERT INTO employees
VALUES (seq.NEXTVAL,
'name',
'last name',
1);
Sometimes, SQL is fancy, because even having a standard (ANSI), most DBMS vendors add their proprietary extensions to the SQL creating their own languages, so it's rare the situation where you can port one SQL from one DB into another without any changes.
Also, it's a pretty useless error message. It could at least say which position. (also, there's no missing parenthesis, but an unexpected token)
EDITED : New feature 12c
CREATE TABLE employees(
id NUMBER GENERATED ALWAYS AS IDENTITY,
first_name VARCHAR2(30)
etc.
);
Why would you do default null?
The VARCHAR datatype is synonymous with the VARCHAR2 datatype. To avoid possible changes in behavior, always use the VARCHAR2 datatype to store variable-length character strings.
Replace
id INT NOT NULL auto_increment PRIMARY KEY (ID),
with
id INT NOT NULL auto_increment PRIMARY KEY,
this is more efficient
CREATE TABLE EMPLOYEES_T(
ID NUMBER,
FIRST_NAME VARCHAR2(20) DEFAULT NULL,
LAST_NAME VARCHAR2(20) DEFAULT NULL,
SALARY INTEGER DEFAULT NULL,
CONSTRAINT PK_EMPLOYEES_T PRIMARY KEY(ID)
);
I'm getting this error in puTTY. Not sure why, looks right to me ...
psql:pierre.sql:10: ERROR: syntax error at or near "AUTO_INCREMENT"
LINE 2: c_id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
^
psql:pierre.sql:18: ERROR: syntax error at or near "AUTO_INCREMENT"
LINE 2: r_id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
--DROP TABLE customer, reservation;
CREATE TABLE customer(
c_id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
c_ref VARCHAR(30) NOT NULL,
f_name VARCHAR(30) NOT NULL,
l_name VARCHAR(30) NOT NULL,
address VARCHAR(100) NOT NULL,
email VARCHAR(100) NOT NULL,
phone VARCHAR(11) NOT NULL
);
CREATE TABLE reservation(
r_id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
c_id VARCHAR(30) NOT NULL REFERENCES customer(c_id),
book_date DATE NOT NULL CHECK (book_date <= now()),
s_time DOUBLE NOT NULL,
e_time DOUBLE NOT NULL,
amount INTEGER NOT NULL
);
Any ideas why?
auto_increment looks like something you'd use with MySQL.
But, here, it seems you are using PostgreSQL.
According to the datatype serial section of the manual, postgresql's equivalent of auto_increment is serial or bigserial.
Quoting that page :
The data types serial and bigserial are not true types, but merely
a notational convenience for setting up unique identifier columns
(similar to the AUTO_INCREMENT property supported by some other databases).
In Postgres 10 or later consider an IDENTITY column:
CREATE TABLE customer(
c_id INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
...
(PRIMARY KEY also makes it NOT NULL automatically.)
Details:
Auto increment table column
In Postgres 9.6 or older consider a serial like Pascal already suggested.
Works in pg 10 or later, too, but IDENTITY is generally superior.