Results of 1 - 10 of about 55 for cases (0.002 sec.)
- Keywords and Identifiers 13467
- Identifiers Similarly to other SQL dialects and programming languages, identifiers in DuckDB's SQL are subject to several rules. Unquoted identifiers need to conform to a number of rules: They must not be a reserved keyword (see duckdb_keyw
...tripped DDL (for example in [ duckdb_views()`](#duckdb_views)) still uses double quotes. Deduplicating Identifiers In some cases, duplicate identifiers can occur, e.g., column names may conflict when unnesting a nested data structure. In these cases,...to them. SELECT col_A FROM (SELECT 'x' AS col_a); -- succeeds SELECT col_á FROM (SELECT 'x' AS col_a); -- fails Preserving cases: While DuckDB treats identifiers in a case-insensitive manner, it preserves the cases of these identifiers. That is, each...character's case (uppercase/lowercase) is maintained as originally specified by the user even if a query uses different cases when referring to the identifier. For example: CREATE TABLE tbl AS SELECT cos(pi()) AS CosineOfPi; SELECT cosineofpi FROM... - https://man.mtool.work/duckdb/2.0/sql/dialect/keywords_and_identifiers.html
- Non-Deterministic Behavior 12270
- Several operators in DuckDB exhibit non-deterministic behavior. Most notably, SQL uses set semantics, which allows results to be returned in a different order. DuckDB exploits this to improve performance, particularly when performing multi-
...erent compilers, operating systems and hardware architectures, can also cause changes in ordering. This page documents the cases where non-determinism is an expected behavior . If you would like to make your queries deterministic, see the “Working Aro...all numbers ( 0 <= z < 10e-16 ) due to floating-point inaccuracies. Working Around Non-Determinism For the majority of use cases, non-determinism is not causing any issues. However, there are some cases where deterministic results are desirable. In th...ese cases, try the following workarounds: Limit the number of threads to prevent non-determinism introduced by multi-threading. sql... - https://man.mtool.work/duckdb/2.0/operations_manual/non-deterministic_behavior.h...
- Text Functions 10910
- Text Functions and Operators This section describes functions and operators for examining and manipulating STRING values . Function Description string[index] Extracts a single character using a (1-based) index . string[begin:end] Extracts a
...(insertions, deletions, substitutions or transpositions) required to change one string to another. Characters of different cases (e.g., a and A ) are considered different. editdist3(s1, s2) Alias for levenshtein . hamming(s1, s2) The Hamming distance...itions with different characters for two strings of equal length. Strings must be of equal length. Characters of different cases (e.g., a and A ) are considered different. jaccard(s1, s2) The Jaccard similarity between two strings. Characters of diffe...rent cases (e.g., a and A ) are considered different. Returns a number between 0 and 1. jaro_similarity(s1, s2[, score_cutoff]) The J... - https://man.mtool.work/duckdb/2.0/sql/functions/text.html
- Caveats 10407
- Equality Comparison Warning Currently, equality comparison of JSON files can differ based on the context. In some cases, it is based on raw text comparison, while in other cases, it uses logical content comparison. The following query retur
... - https://man.mtool.work/duckdb/2.0/data/json/caveats.html
- Tuning Workloads 10067
- DuckDB aims to perform well out of the box, so most workloads do not require any tuning. When tuning is worthwhile, there is no single configuration or magic number that is optimal for every workload: the right settings depend on what you a
...memory, an out of memory error may occur: Out of Memory Error: failed to allocate data of size ... (.../... used) In these cases, consider setting the preserve_insertion_order configuration option to false : SET preserve_insertion_order = false; This...ing ROW_GROUP_SIZE for Parquet files apply verbatim to DuckDB's own database format. Too Many Threads Note that in certain cases DuckDB may launch too many threads (e.g., due to HyperThreading), which can lead to slowdowns. In these cases, it's worth...does attempt to parallelize as much as possible within each individual query, but it is not possible to parallelize in all cases. Making multiple connections can process more operations concurrently. This can be more helpful if DuckDB is not CPU limit... - https://man.mtool.work/duckdb/2.0/guides/performance/how_to_tune_workloads.html
- Overview 8707
- DuckDB's SQL dialect is based on PostgreSQL. DuckDB tries to closely match PostgreSQL's semantics, however, some use cases require slightly different behavior. For example, interchangeability with data frame libraries necessitates order pre
... - https://man.mtool.work/duckdb/2.0/sql/dialect/overview.html
- HTTP(S) Support 8530
- With the httpfs extension, it is possible to directly query files over the HTTP(S) protocol. This works for all files supported by DuckDB or its various extensions, and provides read-only access. SELECT * FROM 'https://domain.tld/file.exten
...sion'; Partial Reading For CSV files, files will be downloaded entirely in most cases, due to the row-based nature of the format. For Parquet files, DuckDB supports partial reading , i.e., it can use a combin...the Parquet metadata and the data for the column_a column: SELECT column_a FROM 'https://domain.tld/file.parquet'; In some cases, no actual data needs to be read at all as they only require reading the metadata: SELECT count(*) FROM 'https://domain.tl... - https://man.mtool.work/duckdb/2.0/core_extensions/httpfs/https.html
- Overview 8530
- We designed DuckDB to be easy to deploy and operate. We believe that most users do not need to consult the pages of the operations manual. However, there are certain setups – e.g., when DuckDB is running in mission-critical infrastructure –
...where we would like to offer advice on how to configure DuckDB. The operations manual contains advice for these cases and also offers convenient configuration snippets such as Gitignore files. For advice on getting the best performance from... - https://man.mtool.work/duckdb/2.0/operations_manual/overview.html
- Writing Tests 8367
- Development and Testing It is crucial that any new features that get added have correct tests that not only test the “happy path”, but also test edge cases and incorrect usage of the feature. In this section, we describe how DuckDB tests ar
...d) be expressed in pure SQL. There are certain exceptions to this, which we will discuss in Catch Tests . However, in most cases you should write your tests in plain SQL. Frameworks SQL tests should be written using the sqllogictest framework . C++ te... - https://man.mtool.work/duckdb/2.0/dev/sqllogictest/writing_tests.html
- Embedding DuckDB 8367
- CLI Client The Command Line Interface (CLI) client is intended for interactive use cases and not for embedding. As a result, it has more features that could be abused by a malicious actor. For example, the CLI client has the .sh feature tha
... - https://man.mtool.work/duckdb/2.0/operations_manual/securing_duckdb/embedding_du...
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