Among popular databases, DB2 is one. Real meanings of some keywords are different from database to database.
DB2 top key words
An SQL which is embedded in application program, you can say as Static SQL. The name itself says that SQL is fixed and it will not vary.
An SQL will be generated or derived based on some conditions given in the application program. It needs more experience. Usually, across all the projects people use Static SQL only. However, SPUFI and QMF where you can execute Dynamic SQL.
Next step to improve DB2 skills
SQL and DB2 Skills Make You King in your Current or Future Projects
An integral part of SQL engine. You no need to give externally in application program. By default, optimiser parses your SQL query.
Optimizer checks Synatx and it decides Optimized path to execute SQL query.
When you have not given or supplied any values, DB2 treats it as NULL value. You can say NULL means lack of value.
Storage of DATE and Time
A DATE takes 4 bytes and Time takes 3 bytes. Combination of these two equal to Timestamp.
Scalar vs Aggregate
Scalar functions you can apply on only one column. Aggregate functions you can apply on group of columns.
Index vs Hashing
Index is a search columns of one or two, database will use to locate data quickly.
Hashing means the values or columns on which you use Hashing are converted to hash value. These values stored in Hash table. Db2 uses hash values to locate your data. The hashing is much faster than indexing.
Triggers are like stored procedures. You can store in database. The DBMS will take care of it when to fire trigger. It is like an event , will happen corresponding to something matching condition happens.
Four types of utilities you can find in DB2.
- Data Consistency
- Data movement
- Backup and Recovery
- Catalog manipulation
Stand Alone Utilities
Only ADMIN can run these. Even when DB2 not active, you can run these utilities. These are purely administrative utilities. Developer has no authority to run these.