Specifies the type of data being stored (string, date, numeric, etc).

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25
votes
5answers
15k views

Performance implications of MySQL VARCHAR sizes

Is there a performance difference in MySQL between varchar sizes? For example, varchar(25) and varchar(64000). If not, is there a reason not to declare all varchars with the max size just to ensure ...
54
votes
3answers
29k views

Advantages and Disadvantages to using ENUM vs Integer types?

Lets say in some random table, you have a column named status. It's real-world values would be either enabled or disabled. Is it better for this column's data type to be an int/bool (1 or zero) or to ...
10
votes
3answers
8k views

Should I add an arbitrary length limit to VARCHAR columns?

According to PostgreSQL's docs, there's no performance difference between VARCHAR, VARCHAR(n) and TEXT. Should I add an arbitrary length limit to a name or address column? Edit: Not a dupe of Would ...
17
votes
1answer
24k views

INT(5) vs SMALLINT(5)

In MySQL table definitions is there a different between INT(5) and SMALLINT(5)? Or do they both represent the same size?
3
votes
1answer
1k views

PostgreSQL SELECT primary key as “serial” or “bigserial”

I've meshed together a way to determine what the data_type is as in the data_type you use in the syntax when creating a new table based off of the PostgreSQL wiki page. If there is something wrong ...
9
votes
2answers
6k views

Data type for storing an array of flags (a bitmap/bit array)

I need to store a bit array for each record of a table, supporting the following operations: Testing if a bit is set, and setting a bit (using SQL) Querying and setting the value using ADO 2.8 (not ...
4
votes
1answer
2k views

How do I decompose ctid into page and row numbers?

Each row in a table has a system column ctid of type tid that represents the physical location of the row: begin; create table t(id serial); insert into t default values; insert into t default ...
22
votes
8answers
10k views

How do long columns impact performance and disk usage?

In our current project it just happens too often, that we need to extend columns by a couple of characters. From varchar(20) to varchar(30) and so on. In reality, how much does it really matter? How ...
5
votes
2answers
9k views

What is the meaning of tinyint(N)?

When we use an argument length with numerical data types, as far as I know this specifies the display width. I tried the following: mysql> create table boolean_test (var1 boolean, var2 tinyint); ...
8
votes
2answers
6k views

Why does “SELECT POWER(10.0, 38.0);” throw an arithmetic overflow error?

I'm updating my IDENTITY overflow check script to account for DECIMAL and NUMERIC IDENTITY columns. As part of the check I compute the size of the data type's range for every IDENTITY column; I use ...
11
votes
2answers
2k views

INT or CHAR for a Type Field

What is the best design for a table, a Type field that is of int or char(1)? In other words, given this schema: create table Car ( Name varchar(100) not null, Description varchar(100) not ...
3
votes
1answer
412 views

SELECT in trigger function in two tables

My table and trigger in PostgreSQL 9.4.3 on x86_64-unknown-linux-gnu, compiled by gcc (Debian 4.9.2-10) 4.9.2, 64-bit: CREATE TABLE measurements ( measurement_id SERIAL PRIMARY KEY NOT NULL, ...
3
votes
1answer
42 views

Why does the behavior of array syntax differ from '(?,?)' syntax when updating a point field and that field is NULL?

I'm using PostgreSQL 9.3.5. Suppose I have the following table: CREATE TEMPORARY TABLE point_test ("name" varchar(255), "pt" point); I then insert a row, leaving pt NULL: INSERT INTO point_test ...
3
votes
2answers
6k views

what is bigger than a longblob?

the longblob is the biggest data type of Mysql. If I want to save something bigger than 4gb (longblob) how can I do?. I'm talking about Mysql v-5.+
0
votes
2answers
108 views

Query that was working on MySQL is not working on PostgreSQL

I had the following query (with bin_number being a string) which was working on MySQL 5.5: Postgres - was working on MySQL and doesn't work on PostgreSQL SELECT "menu_items".* FROM "menu_items" ...
41
votes
3answers
22k views

What are the drawbacks with using UUID or GUID as a primary key?

I would like to build a distributed system. I need to store data in databases and it would be helpful to use an UUID or a GUID as a primary key on some tables. I assume it's a drawbacks with this ...
18
votes
7answers
9k views

Storing IP address

I have to store the IP address of all registered users in the database. I am wondering, how many characters should I declare for such a column? Should I support IPv6 as well? If so, what is the ...
16
votes
2answers
33k views

What is the difference between MySQL VARCHAR and TEXT data types?

After version 5.0.3 (which allowed VARCHAR to be 65,535 bytes and stopped truncating trailing spaces), is there any major difference between these two data types? I was reading the list of ...
21
votes
3answers
23k views

How to combine date and time to datetime2 in SQL Server?

Given the following components DECLARE @D DATE = '2013-10-13' DECLARE @T TIME(7) = '23:59:59.9999999' What is the best way of combining them to produce a DATETIME2(7) result with value '2013-10-13 ...
12
votes
4answers
786 views

Does NULL have a type?

Various sources (eg Wikipedia, PSOUG) state that Oracle's null does not have a type. Is this true? What about other RDBMSs?
6
votes
0answers
144 views

Surprising results for data types with type modifier

While discussing a recursive CTE solution for this question: Get the last 5 distinct values for each ID @ypercube stumbled across a surprising exception, which lead us to investigate the handling ...
5
votes
1answer
281 views

For alignment optimized table is bigger than original table - why?

In another question I learned that I should optimize the layout from one of my tables to save space and have better performance. I did this, but ended up with a larger table than before and ...
4
votes
2answers
745 views

How can I enforce ensure uniqueness of an association with a time dimension?

I have a database table AB which tracks the association of A and B over time: create table AB columns ( ARef ..., -- FK of A BRef ..., -- FK of B Since as Timestamp, Until as Timestamp, ...
3
votes
1answer
68 views

Do fixed-width rows improve PostgreSQL read performance?

I have a table articles: Table "articles" Column | Type | Modifiers | ...
11
votes
2answers
464 views

What is the optimal data type for an MD5 field?

We are designing a system that is known to be read-heavy (on the order of tens of thousands of reads per minute). There is a table names that serves as a sort of central registry. Each row has a ...
5
votes
2answers
926 views

How to best store a timestamp in PostgreSQL?

I'm working on a PostgreSQL DB design and I am wondering how best to store timestamps. Assumptions Users in different timezones will use the database for all CRUD functions. I have looked at 2 ...
4
votes
1answer
246 views

Storing phone number in E.164

TLDR; If I store a phone number in MySQL(or any DB with equivalent constraints), would the correct format be E.164 values into a VARCHAR(32) field? Have been reading up on format/storage of ...
4
votes
1answer
1k views

Do SQL Server Views update their data types automatically based on what tables feed them?

Someone mistakenly created a bunch of nchar fields in database tables. I noticed this, and after examining the issue, we're moving these fields to nvarchar types and trimming the values inside. In my ...
4
votes
2answers
11k views

A Script to insert dummy Data in all tables of Database

I wanted a Script that can loop through all tables and their columns in the database and insert dummy data based on column type and size, so that i can start using the database for testing, and ...
3
votes
1answer
380 views

Good layout of 3d point data for spatial queries in Postgres?

Like shown in another question, I deal with a lot (>10,000,000) entries of points in a 3D space. These points are defined like this: CREATE TYPE float3d AS ( x real, y real, z real); If I am ...
3
votes
1answer
41 views

Is 'internallength' always useful in custom type definition in Postgres?

In our database we use a custom type to store 3D locations: CREATE TYPE float3d AS ( x real, y real, z real); In many examples I see INTERNALLENGTH used as a parameter with the definition of ...
3
votes
1answer
265 views

Use of integer instead of interval (of one type)

Our DB design presently has a interval column which will only be storing days (no other interval type) so it is making sense to use INT2 (smallint) instead of interval. Reference to documentation. ...
2
votes
2answers
179 views

Database events that will cause deletion of index

In SQL server if we try to change a data type of a column having index ,then it deletes the indexes associated with that column and changes the data type . I was not aware of it and was faced problem ...
2
votes
1answer
804 views

Change in datatype?

I have a table on which rows are inserted on hourly basis. The row contains id, installation, product_id and hit_allowed. all of them were mediumint in the beginning. but few days back id reached it ...
2
votes
2answers
5k views

How can I define the datatype of a view in MySQL?

I've written a simple aggregation view over a table, and the view returns different data types that the table. This causes some issues on the application side. Here's a simplified query for the sake ...
1
vote
1answer
55 views

VARCHAR2 should perhaps be DT_WSTR when working with SSIS against a Oracle Database?

When using SSIS with Oracle database, it seems to always assume that a VARCHAR2 maps to a DT_STR. However, if my Oracle encoding is set to AL32UTF8, I should be able to store any unicode character in ...
1
vote
0answers
163 views

Best practice for storing image order number in a database

I am designing a social networking website(mysql with InnoDB engine + php) where I need to store image sequence in a database. The table structure is as follows:- PicId (BIGINT, AUTO INCREMENT, PK) ...
1
vote
1answer
334 views

Function quote_nullable(timestamp without time zone) is not unique

When I run this query on "enterprisedb 9.2", it raises an error: select quote_nullable(to_date('09-02-2014 ','dd-MM-yyyy'))::date; Error: LINE 1: select quote_nullable(to_date('09-02-2014 ...
0
votes
1answer
183 views

Why does mysql give different result for this summations? [duplicate]

Can someone help understand the following behavior? mysql> select (1/3 + 1/3 + 1/3); +-------------------+ | (1/3 + 1/3 + 1/3) | +-------------------+ | 1.0000 | +-------------------+ ...
0
votes
1answer
52 views

What kind of data type to use for numbering in the Harmonized System?

The harmonized system uses a numbering that shows the hierarchy between different items. Similar to bookkeeping ledger numbers. Here is an example: 01 LIVE ANIMALS 0103 swine, live 010310 Purebred ...
0
votes
1answer
2k views

What is the difference between int(8) and int(5) in mysql? [duplicate]

I found out, that if you have a field defined as INT(8) without ZEROFILL it will behave exactly as INT(5) in both cases the maximum value is −2,147,483,648 to 2,147,483,647, from −(2^31) to 2^31 − 1 ...
-1
votes
1answer
883 views

Multiple conditions in a derived column ssis

Hi I am trying fairly new to SSIS , and my task is to convert dates in string as given below to a datetime. These are my date of birth in the source file (string data type): Source date of birth ...