在哪里可以找到 SQL Server 数据类型的大小

Question

I am trying to calculate the size of my database. I will have a table with 3 columns (id, int, money) I will have 26 million rows with all columns being occupied. How big will my database be? Also, where can I find the size of all SQL Server data types?

Answer 1

Your can use below query :

SELECT * FROM sys.types

result of above query is below :

name                 system_type_id user_type_id schema_id principal_id max_length precision scale collation_name    is_nullable is_user_defined is_assembly_type default_object_id rule_object_id is_table_type
-------------------- -------------- ------------ --------- ------------ ---------- --------- ----- ----------------- ----------- --------------- ---------------- ----------------- -------------- -------------
image                34             34           4         NULL         16         0         0     NULL              1           0               0                0                 0              0
text                 35             35           4         NULL         16         0         0     Persian_100_CI_AI 1           0               0                0                 0              0
uniqueidentifier     36             36           4         NULL         16         0         0     NULL              1           0               0                0                 0              0
date                 40             40           4         NULL         3          10        0     NULL              1           0               0                0                 0              0
time                 41             41           4         NULL         5          16        7     NULL              1           0               0                0                 0              0
datetime2            42             42           4         NULL         8          27        7     NULL              1           0               0                0                 0              0
datetimeoffset       43             43           4         NULL         10         34        7     NULL              1           0               0                0                 0              0
tinyint              48             48           4         NULL         1          3         0     NULL              1           0               0                0                 0              0
smallint             52             52           4         NULL         2          5         0     NULL              1           0               0                0                 0              0
int                  56             56           4         NULL         4          10        0     NULL              1           0               0                0                 0              0
smalldatetime        58             58           4         NULL         4          16        0     NULL              1           0               0                0                 0              0
real                 59             59           4         NULL         4          24        0     NULL              1           0               0                0                 0              0
money                60             60           4         NULL         8          19        4     NULL              1           0               0                0                 0              0
datetime             61             61           4         NULL         8          23        3     NULL              1           0               0                0                 0              0
float                62             62           4         NULL         8          53        0     NULL              1           0               0                0                 0              0
sql_variant          98             98           4         NULL         8016       0         0     NULL              1           0               0                0                 0              0
ntext                99             99           4         NULL         16         0         0     Persian_100_CI_AI 1           0               0                0                 0              0
bit                  104            104          4         NULL         1          1         0     NULL              1           0               0                0                 0              0
decimal              106            106          4         NULL         17         38        38    NULL              1           0               0                0                 0              0
numeric              108            108          4         NULL         17         38        38    NULL              1           0               0                0                 0              0
smallmoney           122            122          4         NULL         4          10        4     NULL              1           0               0                0                 0              0
bigint               127            127          4         NULL         8          19        0     NULL              1           0               0                0                 0              0
hierarchyid          240            128          4         NULL         892        0         0     NULL              1           0               1                0                 0              0
geometry             240            129          4         NULL         -1         0         0     NULL              1           0               1                0                 0              0
geography            240            130          4         NULL         -1         0         0     NULL              1           0               1                0                 0              0
varbinary            165            165          4         NULL         8000       0         0     NULL              1           0               0                0                 0              0
varchar              167            167          4         NULL         8000       0         0     Persian_100_CI_AI 1           0               0                0                 0              0
binary               173            173          4         NULL         8000       0         0     NULL              1           0               0                0                 0              0
char                 175            175          4         NULL         8000       0         0     Persian_100_CI_AI 1           0               0                0                 0              0
timestamp            189            189          4         NULL         8          0         0     NULL              0           0               0                0                 0              0
nvarchar             231            231          4         NULL         8000       0         0     Persian_100_CI_AI 1           0               0                0                 0              0
nchar                239            239          4         NULL         8000       0         0     Persian_100_CI_AI 1           0               0                0                 0              0
xml                  241            241          4         NULL         -1         0         0     NULL              1           0               0                0                 0              0
sysname              231            256          4         NULL         256        0         0     Persian_100_CI_AI 0           0               0                0                 0              0
CalculatedCreditInfo 243            257          9         NULL         -1         0         0     NULL              0           1               0                0                 0              1
udt_QoutaDetail      243            258          21        NULL         -1         0         0     NULL              0           1               0                0                 0              1
BeforeUpdate         243            259          22        NULL         -1         0         0     NULL              0           1               0                0                 0              1
udt_StoreInventory   243            260          26        NULL         -1         0         0     NULL              0           1               0                0                 0              1
udt_WKFHistory       243            261          32        NULL         -1         0         0     NULL              0           1               0                0                 0              1
IDTable              243            262          1         NULL         -1         0         0     NULL    

you can use max_length for size of each data type.

Answer 2

T-SQL has a function for that: DATALENGTH for all SQL Server versions.

Example:

DECLARE @lat DECIMAL(10, 7) = 3.14151415141514151415;

SELECT @lat, DATALENGTH(@lat);

Result: 3.1415142 and 5 (because DECIMAL(10,7) uses 5 bytes to be stored).

Documentation: https://docs.microsoft.com/en-us/sql/t-sql/functions/datalength-transact-sql?view=sql-server-ver15

For example, I have a table called Applications with these columns: ( id VARCHAR(32), debug BIT, connectionString VARCHAR(2048), firebaseKey VARCHAR(4096) ). As we know, VARCHAR doesn't allocate all the space (just what you need, so 'A' is 1 byte in VARCHAR).

These queries:

SELECT 
  SUM(DATALENGTH(id)) AS idSize,
  SUM(DATALENGTH(debug)) AS debugSize,
  SUM(DATALENGTH(connectionString)) AS connectionStringSize,
  SUM(DATALENGTH(firebaseKey)) AS firebaseKeySize
FROM Applications;

SELECT 
  SUM(
    DATALENGTH(id) +
    DATALENGTH(debug) + 
    DATALENGTH(connectionString) +
    DATALENGTH(firebaseKey)
  ) AS totalSize
FROM Applications;

will return my data size (in my case, with my rows, is 8, 2, 366, 4698 (total: 5074). There are 2 rows in that table.

Notice that this does NOT represent the total size of my database (there are pages, descriptors, indexes, etc. involved.) *

MSSQL has internal stored procedures to tell you the exactly size of your database in disk:

• EXEC sp_spaceused; for all database;
• EXEC sp_spaceused N'schema.TableName'; for a specific table;
• EXEC sp_helpdb N'DatabaseName'; if you want details from each file.

Answer 3

http://msdn.microsoft.com/en-us/library/ms187752.aspx

Money : 8 bytes
int : 4 bytes
id  - depends on what you mean.

Answer 4

If the table specified in the where clause contains a nvarchar, this query will give you how many characters there are for that column correctly!

This detects if the column is "wide" and essentially divides by 2. More broad than just nvarchar.

SELECT c.name, (CASE WHEN LEFT(ts.name, 1) = 'n' AND ts.[precision] = 0 AND ts.[scale] = 0 THEN c.max_length / ts.[bytes] ELSE c.max_length END) AS [length]
FROM sys.columns AS c
    INNER JOIN sys.tables AS t
        ON t.object_id = c.object_ID
    INNER JOIN
    (
        SELECT *, (CASE WHEN [bits] = -1 THEN -1 ELSE ([bits] + 7) / 8 END) AS [bytes]
        FROM (
            SELECT *, (CASE WHEN max_length >= 256 THEN (CASE WHEN LEFT(name, 1) = 'n' AND [precision] = 0 AND [scale] = 0 THEN 16 ELSE 8 END) ELSE max_length END) AS [bits]
            FROM sys.types AS iits
        ) AS its
    ) AS ts
        ON ts.user_type_id = c.user_type_id
WHERE t.name LIKE 'tb_tablename' -- LIKE is case insensitive

Of course, you can just divide max_length on sys.columns by 2 if you know the column is an nvarchar. This is more for discovering table schema in a way that seems better for if new sql data types are introduced in the future. And you so-choose to upgrade to it. Pretty small edge case.

Please edit and correct this answer if you find an edge case where bytes and bits are incorrect.

Details:

-- ([bits] + 7) / 8 means round up
--
-- Proof:
--   o  (1 bit + 7 = 8) / 8 = 1 byte used
--   o  ((8 + 8 + 1 = 17 bytes) + 7 = 24) / 8 = 3 byes used
--   o  ((8 + 8 + 7 = 23 bytes) + 7 = 30) / 8 = 3.75 = integer division removes decimal = 3
SELECT *, (CASE WHEN [bits] = -1 THEN -1 ELSE ([bits] + 7) / 8 END) AS [bytes]
FROM (
    SELECT *, (CASE WHEN max_length >= 256 THEN (CASE WHEN LEFT(name, 1) = 'n' AND [precision] = 0 AND [scale] = 0 THEN 16 ELSE 8 END) ELSE max_length END) AS [bits]
    FROM sys.types AS its
) AS ts

If someone knows that SQL Server stores the bit and byte sizes for each data type. Or a better way to get sys.columns size, please leave a comment!