* MSSQL three key system tables

sysdatabases system table: each database on Microsoft SQL Server occupies one row in the table. When you first Install SQL Server, sysdatabases contains the master, model, MSDB, mssqlweb, and tempdb database items. The table is only stored in the master database. This table is saved in the master database. What information is saved in this table? This is very important. It stores all the database names, as well as the database IDs and related information.
here I will list the useful field names and descriptions. Name // indicates the name of the database.
dbid // indicates the database ID. dbid ranges from 1 to 5. These databases are master, model, MSDB, mssqlweb, and tempdb respectively. Select * from Master. DBO. sysdatabases to query all database names.

Sysobjects: each database in the SQL-SERVER has this system table, which stores all the objects created in the database, such as constraints, default values, logs, rules, stored procedures, etc, each object occupies one row in the table. The following table describes the field names and descriptions of the system table.
Name, ID, xtype, uid, status: Object Name, Object ID, object type, user ID of the owner object, and object status.
Object Type (xtype ). It can be one of the following object types:
C = check Constraints
D = default value or default Constraint
F = foreign key constraint
L = Log
Fn = scalar function
If = embedded table functions
P = Stored Procedure
PK = primary key constraint (type: K)
Rf = copy and filter the Stored Procedure
S = system table
TF = table functions
Tr = trigger
U = User table
Uq = unique constraint (type is K)
V = View
X = Extended Stored Procedure
When xtype = 'U' and status> 0 indicates that the table is created by the user, the object name is the table name, and the Object ID is the table id value.
Use: Select * From chouyfd. DBO. sysobjects where xtype = 'U' and status> 0 to list the table names created by all users in chouyfd.

Syscolumns: each column in each table and view occupies one row in the table, and each parameter in the stored procedure occupies one row in the table. The table is located in each database. The main fields are:
Name, ID, colid: The field name, table ID, and field ID respectively. The ID is the ID of the table we just obtained using sysobjects.
Select * From chouyfd. DBO. syscolumns where id = 123456789.