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| author | Julian T <julian@jtle.dk> | 2022-01-12 08:58:34 +0100 |
|---|---|---|
| committer | Julian T <julian@jtle.dk> | 2022-01-12 08:58:34 +0100 |
| commit | 2b780bf79aa3b5d835442687b76ad3c42b2ce44a (patch) | |
| tree | 16978fae6f80fb22215a7a8db5c6dbdb1fe4d8de | |
| parent | 73824760a31860d93ae9818a094ad5cef9037f8d (diff) | |
ETL notes
| -rw-r--r-- | sem7/db/eksamnen.md | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/sem7/db/eksamnen.md b/sem7/db/eksamnen.md index d9386db..5c6da48 100644 --- a/sem7/db/eksamnen.md +++ b/sem7/db/eksamnen.md @@ -2,12 +2,14 @@ # TODO - Lav opgave 2.3 i distributed thing + - Læs om view maintenance # Words and Things - **ROLAP**: Relational Online Analytical Processing - *Summarizability* on page 52 in DW book. - *Data marts* is a subset of a data wareshouse, containing only as single subject such as sales. + - *Heterogeneity* page 19 in parallel book # Nice Spatial SQL Commands @@ -427,6 +429,8 @@ This should therefore not be used for user queries. Here large sequential operations are done to transform data, in a process that should be easy to restart etc. When done data can be copied to data marts. +Slide 25 giver en plan for at opstille en ETL plan. + ## Extract Data can either be copied from **cooperative sources** such as replication mechanism, or call backs. @@ -441,3 +445,11 @@ This process of finding deltas is called **changed data capture** (CDC), where o This can be data convertions such as string encoding or data/time representation. +This also related to **data quality**. +Slide 14 states some requirements for data in DW. + +## Load + +SQL is often slow for loading into DW. +If used the index should be dropped and reindexed after loading. + |